NOISE ELEMENT
of the
THOUSAND OAKS GENERAL PLAN
May, 2000
City of Thousand Oaks
Department of Planning and Community Development
2100 Thousand Oaks Boulevard
Thousand Oaks, CA 91362
Adopted by City Council May 16, 2000
CBA Job#: 1018.00
Thousand Oaks General Plan
Noise Element
THOUSAND OAKS GENERAL PLAN
NOISE ELEMENT
CITY COUNCIL
Dennis C. Gillette, Mayor
Daniel A. Del Campo, Mayor Pro Tem
Andrew P. Fox
Michael S. Markey
Linda Parks
PLANNING COMMISSION
David Anderson, Chair
Thomas Glancy, Vice Chair
Jim Bruno
Michael Farris
John Powers
STAFF
Lawrence Marquart, Senior Planner
Nancy Kierstyn Schreiner, Assistant City Attorney
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CONTENTS
Tables......................................................................................................................... ............. iii
Figures ............................................................................................................................... ..... iii
1. Introduction................................................................................................................... ....... 1
Legislative Requirements ....................................................................................................... 1
Updated Element.................................................................................................................... 1
1. Issues, Problems and Opportunities ...................................................................................... 3
1.1. Noise as a Public Policy Issue in Thousand Oaks. .............................................................. 3
1.2. Describing the Noise Environment. .................................................................................... 4
1.2.1. Descriptors of Instantaneous Sound Level................................................................... 7
1.2.2. Energy- averaged Noise Descriptors............................................................................. 9
1.2.3. Time- of- Day Weighted Noise Descriptors................................................................... 9
1.3. Noise Standards and Guidelines ....................................................................................... 10
1.4. Existing and Potential Future Noise Problems in Thousand Oaks..................................... 14
1.4.1. Community Noise Concerns ...................................................................................... 14
1.4.2. Community Noise Survey........................................................................................... 14
1.4.3. Motor Vehicle Noise Impact....................................................................................... 21
2. Goals and Objectives ........................................................................................................... 29
Goal N- 1. Achieve and maintain an environment in which noise- sensitive uses are not
disturbed by noise that exceeds exposure guidelines established in this Noise Element.... 29
Goal N- 2. Preserve quiet and diminish existing noise levels in areas of noise- sensitive uses
to the extent reasonable and feasible while permitting development in accordance with the
Land Use and Circulation Elements of the General Plan. ...................................................... 30
3. Solving Noise Problems ....................................................................................................... 31
3.1. Noise Control Strategies................................................................................................... 31
3.1.1. Noise Control at the Noise Source............................................................................. 31
3.1.2. Reducing Motor Vehicle Noise at the Noise Source.................................................... 31
3.1.3. Noise Control in the Noise Path................................................................................. 39
3.1.4. Noise Control at the Receiver..................................................................................... 39
4. Quiet City Program............................................................................................................... 44
4.1. Land Use Planning Standards........................................................................................... 44
4.2. Interior Noise and Sound Insulation Standards................................................................. 45
4.3. Arterial Street Noise Abatement Program. ........................................................................ 46
4.3.1. Rubberized Asphalt Treatment Program..................................................................... 46
4.3.2. Arterial Roadway Noise Barrier Wall Program.............................................................. 46
4.3.3. Arterial Roadway Sound Insulation and Noise Barrier Mitigation Program.................. 52
4.3.4. Noisy Vehicle Code Enforcement Program. ................................................................ 52
4.3.5. Arterial Roadway Speed Control ................................................................................. 53
4.4. Noise Review of Project Time Extensions. ........................................................................ 53
4.5. Freeway Noise Barrier Wall Completion Program............................................................... 54
4.5.1. Caltrans Noise Barrier Construction Advocacy and Monitoring................................. 54
4.5.2. Legislative Advocacy of Caltrans Noise Barrier Funding Increases............................ 55
4.5.3. Freeway Noise Barrier Construction .......................................................................... 55
Figure 8: Back page ................................................................................................................. 57
4.6. Noise Considerations in Environmental Impact Reports and Negative Declarations......... 58
4.6.1. Thresholds of Significant Project and Cumulative Noise Impact................................ 58
4.6.2. Mitigation Measures................................................................................................... 59
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Noise Element
4.7. Nuisance Noise Control - Noise Ordinance..................................................................... 60
4.8. Noise in City Purchasing and Contracting......................................................................... 61
4.9. Noise in Public Construction Projects............................................................................... 61
5. Glossary ............................................................................................................................... 62
Appendix A. Noise Standards and Guidelines
Appendix B. Noise Abatement Strategies from California Office of Noise Control
Noise Element Guidelines
iii
Tables
Table 1. Characteristics of Noise ................................................................................................. 5
Table 2. Noise Levels for Common Noise Sources ....................................................................... 8
Table 3. EPA Health and Welfare Criteria for Noise..................................................................... 11
Table 4. Noise Problems Identified at Public Meetings............................................................... 19
Table 5. Existing and Proposed Land Use in Traffic Noise Impact Areas .................................... 23
Table 6. Outline of Potential Noise Abatement Strategies .......................................................... 35
Table 7. Noise Abatement Strategies: Costs, Effectiveness, Other Considerations .................... 36
Table 8. Sound Insulation Retrofit Cost Estimates ..................................................................... 41
Table 9. Thresholds of Significance for Noise Impact ................................................................ 58
Table 10. Adding Noise Levels in Decibels.................................................................................. 64
Figures
Figure 1. Standards for Land Use Compatibility with Urban Noise Environments........................ 13
Figure 2. Community Noise Monitoring Summary ....................................................................... 17
Figure 3. Existing Freeway and Arterial Street Traffic Noise Levels. ............................................ 25
Figure 4. Projected Future Freeway and Arterial Street Noise Levels............................................ 27
Figure 5. Noise as a Function of Vehicle Speed........................................................................... 33
Figure 6. Condition of Existing Arterial Roadway Walls............................................................... 48
Figure 7. Noise Abatement Effectiveness of Arterial Barrier Walls ............................................... 50
Figure 8. Existing and Proposed Freeway Noise Barriers.............................................................. 56
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1. Introduction
People consider noise an important factor in the quality of life in any community. Based on information
contained in this Noise Element, the City of Thousand Oaks finds that achieving and maintaining a
quiet environment is important to maintaining the character and quality of the City, and is an appropri-ate
subject for City policy, City programs, and the establishment of local regulations.
Legislative Requirements
The State of California requires that each city and county prepare a noise element as part of its general
plan. The California Government Code, Section 65302 ( f), requires the general plan to include:
A noise element which shall identify and appraise noise problems in the community. The noise ele-ment
shall recognize the guidelines established by the Office of Noise Control in the State Department
of Health Services and shall analyze and quantify, to the extent practicable, as determined by the legis-lative
body, current and projected noise levels for all of the following sources:
1. Highways and freeways.
2. Primary arterials and major local streets.
3. Passenger and freight on- line railroad operations and ground rapid transit systems.
4. Commercial, general aviation, helicopter, helistop, and military airport operations, aircraft
overflights, jet engine test stands, and all other ground facilities and maintenance functions
related to airport operation.
5. Local industrial plants, including, but not limited to, railroad classification yards.
6. Other ground stationary noise sources identified by local agencies as contributing to the
community noise environment.
Updated Element
This Noise Element is a comprehensive update of the Noise Element of the Thousand Oaks General
Plan. The Noise Element of the Thousand Oaks General Plan was adopted in 1974, and the current ver-sion
of the Noise Element was adopted by the City Council in September, 1987. In preparing the Noise
Element update, the City involved the public in workshops to identify noise issues and review draft
policies. Consultants were engaged to conduct noise monitoring, evaluate noise problems ( including
updating existing and projected noise contours) and to recommend changes to the policies of the
Noise Element and the City’s Noise Ordinance. City staff from the Community Development Depart-ment
and Public Works Department participated extensively with the consultant team in preparation of
the draft revised Noise Element prior to its release for public review. The Draft Element was reviewed
by the public prior to action by the Planning Commission and City Council.
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1. Issues, Problems and Opportunities
1.1. Noise as a Public Policy Issue in Thousand Oaks.
Thousand Oaks is a suburban community that seeks to maintain a high quality of life for its residents.
A noisy environment detracts from this quality of life.
The City’s General Plan states the following goal for environmental quality:
• To provide a high quality environment, healthful and pleasing to the senses, which values the re-lationship
between maintenance of ecological systems and the people’s general welfare. ( Council
Resolution 97- 8)
Minimizing noise is an important aspect of achieving an environment that is both healthful and pleas-ing
to the senses.
By far the most important noise source in Thousand Oaks, based both on residents’ expressed con-cerns
and on the number of people exposed to the highest average noise levels, is motor vehicle traffic
on the City’s arterial streets and freeways. Because the City is at a substantial distance from the air-ports
serving the region, it is not substantially affected by aircraft noise. Although the Federal Aviation
Administration ( FAA) has established helicopter routes along local freeways, these routes are not heav-ily
used, and overflights are not normally at low altitude. No rail line traverses the City, and rail noise
is not an issue in Thousand Oaks.
Other noise problems that have arisen occasionally in the City include noise at the interface between
residential and commercial or industrial land uses. These problems typically result from deliveries, es-pecially
at unusual hours, or manufacturing or repair processes involving noisy equipment.
Noise problems also result from people’s daily activities. Such noise sources as amplified sound ( ra-dios,
stereos, television, particularly outdoors or between units in multifamily structures), use of loud
equipment such as lawn mowers, leaf blowers, power tools; residential equipment such as air condi-tioner
compressors, pool pumps and fans; and nuisance noises on private property, such as shouting,
use of vehicles, alarms, and so on, all have the potential to result in noise problems.
Noise becomes a public policy issue of concern to the City when noise affects the public health and
welfare, or when noise results from actions by the City. Examples of such cases include:
Noise which results directly or indirectly from the construction and operation of new residential,
commercial and industrial projects which are approved by the City, the construction of public fa-cilities,
or operation of public services.
Private actions which result in noise on other properties sufficient to cause substantial annoyance
or disruption of activities.
Noise sources which have a substantial adverse impact on the quality of life for City residents.
Depending on the potential for noise regulation to affect interstate or international commerce, some
noise problems may be regulated by other levels of government. For example, in order to minimize the
potential problems that might result if each state established standards for newly manufactured air-craft,
the federal government has preempted the establishment of such standards by states and local
agencies.
Similarly, noise standards for protection of employee health have typically been set by the state and
federal governments in order to ensure that such standards protect the entire population.
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The existing structure of the regulatory scheme for various noise sources is outlined in Appendix A,
Noise Standards and Guidelines of Other Agencies, of this Noise Element.
1.2. Describing the Noise Environment.
Noise is often defined as annoying or unwanted sound. In order to define noise problems and to es-tablish
a regulatory scheme to deal with noise that is both fair and effective, it is necessary to under-stand
some of the basic characteristics of sound and how it affects people and their activities. Some of
the most important characteristics are identified briefly in Table 1 on page 5. This table also provides
general comments about how these characteristics are considered in planning.
While sound levels can be easily measured, the variability in subjective and physical response to sound
complicates the analysis of its impact on people.
Sound is created when an object vibrates and radiates part of its energy as acoustic pressure waves
through a medium such as air, water, or a solid. The ear, the hearing mechanism of humans and most
animals, receives these sound pressure waves and converts them to neurological impulses which are
transmitted to the brain for interpretation. The interpretation by the auditory system and the brain de-pends
on the characteristics of the sound, and on the characteristics of the person hearing it.
There are two parameters that are used technically to describe the sound environment at any instant in
time: amplitude ( or sound power) and frequency ( or pitch). These two characteristics affect the way
people respond to sound.
Amplitude of a sound is a measure of the pressure or force that a sound can exert. Subjectively, we
say a sound is louder if it has a greater amplitude than another sound. Thus the amplitude of sounds
can be described either in measurable magnitude or in relative terms of loudness.
Physically, sound pressure is measured in units of decibels ( dB). The sound pressure scale is based on
the ratio of the energy of the sound energy to a reference pressure which is approximately the least
sound pressure that people can perceive. Zero dB means the lowest level normally audible, but does
not mean zero sound pressure.
Frequency of a sound is expressed in units of cycles per second, or Hertz ( Hz), referring to the num-ber
of times per second the acoustic pressure wave peaks. Subjectively, a sound that has more cycles
per second than another is higher pitched. The human hearing system is not equally sensitive to sound
at all frequencies, and is most sensitive to sounds in the frequency range of human speech, from 400
to 2000 cycles per second. The most sensitive people can hear sounds ranging from a little below 20
Hz to somewhat above 20,000 Hz. As people age, their sensitivity to high frequencies tends to fall.
Acoustical energy at frequencies above the range of human hearing is referred to as ultrasonic, or ul-trasound.
At frequencies below the range of human hearing, acoustical energy is referred to as infra-sonic,
or infrasound, and is experienced as vibration.
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Table 1. Characteristics of Noise
Noise
Characteristic
What is Measured,
Units of Measurement
Effects on People and Human Activities
Loudness or
Sound Pressure
Energy content of sound waves
in the air. Unweighted sound
pressure level in decibels ( dB)
Noise distracts attention from tasks, interferes
with verbal communication, and prevents or dis-turbs
sleep. At high levels or for long periods,
noise causes temporary or permanent hearing
loss. At very high levels, noise causes pain.
Louder sounds have greater effects, subject to the
further considerations below.
Frequency or Pitch Frequency ( cycles per second, or
Hertz ( Hz) of pressure waves.
Frequency distribution by octave
or 1/ 3 octave band. Overall
sound pressure level weighted
by frequency, such as A-weighting
( dB( A))
The human ear is most sensitive to sounds in the
range of human speech, less sensitive to high or
low frequencies at the same sound energy.
Tonal content Pure tones or energy distribution
by octave or 1/ 3 octave fre-quency
band. Special weight-ings
such as Effective Perceived
Noise Level in decibels ( EPNDB),
or simple penalty weightings for
pure tones.
High tonal content means identifiable whines or
hums, which can be particularly annoying com-pared
to random noise of the same sound energy.
Information con-tent
( music, voice,
sirens, etc.)
Judgement that sound includes
voice, music, etc. No standard
measurement scheme or
weighting.
Information content draws attention to sounds
compared to more random noise of the same
sound energy.
Impact noise Rapid increase in sound pres-sure
or repetitive impacts. Fast
response on sound meters used
to measure impact noise.
Impact noise ( helicopter rotor blade noise, jack-hammers,
etc.) can be more annoying than other
noises of the same sound energy.
Duration of noise
events as per-centage
of 24-
hour or other pe-riod.
Hourly or other time- averaged
energy level ( Leq) or statistical
sound levels identifying the level
exceeded a given percentage of
the time ( L10, L50)
A noise which lasts longer or is constant has more
impact than one of the same sound energy that
occurs only occasionally or for a short period of
time.
Degree of intru-sion
of noise
events over back-ground
noise lev-els
Difference between peak and
ambient noise levels. Statistical
sound levels, peak noise levels
compared to average or ambi-ent.
Individual distinct noise events such as aircraft
overflights or loud vehicle passby events of a
given noise level are more intrusive if they occur in
a quiet environment.
Time of day 24- hour or annual average level
with weightings for evening and
night noise such as CNEL or Ldn.
People and their activities are generally more sen-sitive
to noise during the nighttime hours because
( 1) background noise is generally lower, making
noise of a given noise level more intrusive, and ( 2)
sleep is easily interrupted by noise.
Importance of
noise source
Judgement of social value of
noise source.
People are generally willing to accept more dis-turbance
from noise they consider necessary, such
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Noise Element
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as from trash collection, emergency vehicle sirens,
police helicopters, etc.
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1.2.1. Descriptors of Instantaneous Sound Level.
The simplest measures of sound are those that measure the loudness or energy content of sound at
any given instant. These measures include the Sound Pressure Level, which is unweighted for fre-quency,
and various weighted noise level measures intended to better reflect the response of the hu-man
ear and brain. Most agencies using noise descriptors to establish community noise standards,
including the State of California, the U. S. Environmental Protection Agency, Caltrans, and other agen-cies
throughout the world, use the A- weighted sound level as the basis for these standards.
The A- weighted sound level scale has been developed to measure sound in a manner similar to the
way the human hearing system responds. The use of the A- weighted scale is often indicated by using
the abbreviation “ dB( A)” for expressing the units of the sound level. Typical A- weighted sound levels
measured for various common noise sources are provided in Table 2 on page 7.
Adding noise values. Because the units describing sound levels are logarithmic, they cannot be
added arithmetically. For example, two noise sources, each of which results in a noise level of 60
dB( A), when combined result in a doubling of the amount of acoustical energy in the environment. This
doubling results in an increase of only approximately three decibels in the sound level, to 63 decibels.
Because of the large difference in energy represented by a small change in noise level, adding two noise
sources of substantially different levels has little impact on the level determined by the louder of the
two sources. For example, adding one noise source at 70 decibels to a source at 60 decibels produces
a total noise level of 70.4 decibels. Table 10 on page 61 provides a quick shortcut to adding noise lev-els
from multiple noise sources, and estimating the change in noise level that results from a change in
intensity of a noise source ( such as traffic noise) composed of a number of individual noise sources.
Significance of changes in noise level. Acousticians have determined that individuals cannot
reliably tell the difference between the noise level of two sounds heard close to each other in time
unless the sound levels differ by three decibels or more. People generally find that an approximately
10- decibel increase in sound level is necessary before the sound is judged to be twice as loud.
These findings based on single short individual noise events in a laboratory situation cannot be applied
to community noise environment situations which are made up of millions of such individual noise
events over a typical year. A three- decibel increase in the energy- averaged noise level means twice as
many noise events in the environment, or louder events, so that noise has a higher probability of dis-rupting
noise- sensitive activities over a day or year. The following additional factors must be consid-ered
in evaluating the impacts of small numeric changes in annual average noise levels:
1. Even a small increase in average noise level such as by 1 to 3 decibels may mean that speech and
other activities are disrupted more often, or for more people, over any given period of time.
2. In some instances, a small increase in average noise level may mean that people and noise-sensitive
land uses in a substantially larger area are exposed to noise levels exceeding a threshold
of significant effect.
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Table 2. Noise Levels for Common Noise Sources
Peak Noise
Level ( dB( A))
Common Indoor Noise Sources
Common Outdoor Noise Sources
Greater than 110 Rock Band
105- 110
100- 105 Military jet flyover at 1,000 feet
95- 100 Inside subway train Gas lawn mower at 3 feet
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1.2.2. Energy- averaged Noise Descriptors.
Many studies have been conducted over the years in an effort to identify the best single noise environ-ment
descriptor which would predict people’s reaction to the widely varying and different noise envi-ronments
in urban areas. Such studies have found that noise descriptors which average the instanta-neous
noise levels over the time period of analysis result in the best correlation with people’s assess-ment
of the impact of noise on their environment and quality of life for most typical urban noise envi-ronments.
The energy- average noise level is the constant noise level that would result if the total
sound energy received over the measurement period from varying noise levels was received as a con-stant
level over the entire measurement period. The energy- average noise level has the advantage that
it considers all the principal factors that result in annoyance in a single number:
1. The energy- average noise level is strongly dependent on the noise level of the few loudest noise
events, which are likely to cause the greatest interference with normal day- to- day activities and cause
the greatest annoyance.
2. The energy- average noise level increases both with the number of noise events of the same noise
level, and with the loudness of individual noise events.
3. The energy- average noise level has been found to correlate well with people’s overall reaction to
noise environments, consistently comparing people’s responses to environments with a few noise
events of high noise level to their response to environments with a large number of noise events of
lower noise level.
Equivalent Noise Level. ( Leq) The equivalent noise level is the average noise level averaged over
any reference period of time. The most common averaging period is one hour, sometimes denoted
Leq( 1). Leq( 24) is also often used to represent the average noise level over a 24- hour day. Unless other-wise
indicated, the Leq is typically assumed to be based on the A- weighted noise level.
Single Event Level ( SEL). The Single Event Level is the energy- averaged noise level of a noise event
such as a vehicle passby or an aircraft overflight, normalized to a time of one second. This is level that
would be measured in one second if all the sound energy of the noise event, from the time it rises
above the background noise level until the time it fades into the background again, were concentrated
in one second. This convention allows the convenient logarithmic adding and multiplying of SEL values
to calculate total daily noise exposure from a variety of noise events.
1.2.3. Time- of- Day Weighted Noise Descriptors.
People and their activities are more sensitive to noise at night, both because more people are at home
involved in quiet activities or sleeping, and because background noise levels are lower, making intru-sive
noises more obvious. The attempt to find a single noise level which represents all aspects of the
noise environment that affect people has therefore resulted in the definition of time- weighted noise
levels. These noise measurement schemes add a weighting to the energy- averaged noise level for
noise during periods of higher noise sensitivity.
Community Noise Equivalent Level ( CNEL) and Day- Night Level ( Ldn). Two different time-weighted
noise measures are important for assessing noise in Thousand Oaks. The first is the Day-
Night level, or Ldn, used by the Environmental Protection Agency, other federal agencies and most
states in regulating community noise. Second is the Community Noise Equivalent Level, or CNEL, which
is used in California regulations and guidelines related to noise impact and sound insulation.
Both the CNEL and Ldn include a 10- decibel penalty for noise that occurs between 10: 00 P. M. and 7: 00
A. M. The CNEL includes an additional 5- decibel penalty for noise that occurs between 7: 00 P. M. and
10: 00 P. M.
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1.3. Noise Standards and Guidelines
This section of the Noise Element provides technical background on the nature of noise problems, pro-vides
the justification for establishment of noise standards and regulation of noise sources, and estab-lishes
specific noise guidelines for land use compatibility
Variation in Human Response to Noise Environments. The use of any single noise descriptor to
regulate noise must be considered in light of a wide variation in people’s response to the character of
the noise environment. In any given situation of noise impact, there is likely to be found a wide range
of response, including both people who do not consider the noise to be at all important, and people
who consider the noise to be unusual and severe. Regardless of the noise situation, there may be 10 to
20% of the total population in each of these extreme categories. In establishing noise standards,
acousticians and social scientists have used the point where a substantial part of the population begins
to shift out of the group that considers noise not to be an issue as the point where noise should be
considered to have an adverse effect on people and their activities. They have used that point where a
substantial portion of the population begins to shift into the group considering the noise to be unusual
and severe as the point at which the noise environment should be considered unacceptable for residen-tial
areas.
Noise Standards and Guidelines of Other Agencies. Table 3 on the following page summarizes
U. S. Environmental Protection Agency health and welfare noise guidelines. Standards and guidelines of
a number of other agencies are listed and discussed in Appendix A.
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Table 3. EPA Health and Welfare Criteria for Noise
Effect
Noise Level Needed to Pro-tect
the
Public Health and Welfare
with an Adequate Margin of
Safety Area
Hearing Loss Leq ( 24) < 70 dB All areas.
Ldn < 55 dB Outdoors in residential areas and farms and
other outdoor areas where people spend
widely varying amounts of time and other
places in which quiet is a basis for use.
Outdoor activ-ity
interference
and
annoyance Leq ( 24) < 55 dB Outdoor areas where people spend limited
amounts of time, such as school yards,
playgrounds, etc.
Indoor activity Leq < 45 dB Indoor residential areas.
interference
and
annoyance
Leq ( 24) < 45 dB Other indoor areas with human activities
such as schools, etc.
Response to noise Threshold of effect
Hearing Loss Leq( 24) not to exceed 65 for long periods ( minimum 1 year) for 100%
confidence
Communication Interference Varies with background sound level. For normal speaking voice at 3
feet to achieve 70% word intelligibility, the background level should be
65 dBA or less.
Sleep Interference Maximum levels should not exceed 70 dBA. The differential with the
ambient should not exceed 10 dBA. for probability of 70% that waking
will not occur.
Stress Factors No clear criteria to date.
Annoyance Threshold for “ highly annoyed” in residential areas at Leq( 24) =
55dBA
Significant change in sound
level for individual noise
events
3 to 5 dBA
Audibility Generally, the onset is 5 dBA below the instantaneous ambient
Source: U. S. Environmental Protection Agency, Report on Levels of Environmental Noise Requisite to Protect the
Public Health and Welfare with an Adequate Margin of Safety, 1974.
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Noise Standards for Land Uses in Thousand Oaks. Figure 1 on page 12 is a summary of noise
standards and guidelines for acceptability of outdoor environmental noise levels for various land uses
based on a large number of these studies over the years. The standards are generally consistent with
the findings and recommendations of the EPA Levels Document, standards of the U. S. Department of
Housing and Urban Development, the California Airport Noise Standards and the California standards
for sound insulation of residential units. The standards are based closely on the recommended stan-dards
of acceptability included in the California Health Department Office of Noise Control’s guidelines
for noise elements, which were used without change in the City’s 1987 Noise Element. Some adjust-ments
have been made in those recommendations to eliminate ambiguities and to tailor the guidelines
for the City of Thousand Oaks, as described below under “ Changes from Standards of the 1987 Noise
Element.”
These standards are established by this Noise Element as the appropriate standards for different types
of land use in the City of Thousand Oaks. Where noise problems exist, appropriate strategies should
be applied to reduce noise problems.
Noise- Sensitive Land Uses. The term “ noise- sensitive land uses” is used throughout the Noise
Element to refer to land uses that are particularly sensitive to noise at levels commonly found in the
urban environment. Within the Noise Element, the term “ noise- sensitive land use” is considered to in-clude
all uses in Figure 1 for which the “ normally unacceptable” impact category begins at a noise level
of 70 dB CNEL or less. This category includes all residential uses, schools, hospitals, churches, out-door
spectator sports facilities, performing arts facilities, and hotels and motels.
Changes from Standards of 1987 Noise Element. Adopted standards established in the 1987
Noise Element have been modified in the following ways:
The ambiguity caused by the overlap between the category of “ normally acceptable” and “ conditionally
acceptable” in the 1987 Noise Element has been eliminated. A specific noise level above which the
noise environment is considered “ normally unacceptable” is established for most land uses, and the
“ clearly acceptable” category is added to include those noise levels below which the noise environment
would normally be considered to present no problems for the specified land uses.
The noise level considered “ normally unacceptable” for residential development has been reduced to 65
dB CNEL for all categories of residential land use. The previous Noise Element considered 70 dB CNEL
to be the threshold of the “ normally unacceptable” area for residential land uses. This change reflects a
concern for the quality of the outdoor noise environment in all residential areas, and is the City’s cur-rent
practice in reviewing development projects.
Limitations on Use of Land Use Compatibility Standards . These new standards are intended to
be used for land use planning at the citywide, specific plan, or project planning level. They indicate the
sensitivity of land uses to the overall noise environment from all sources, which is typically dominated
by urban transportation noise sources. These standards have limited applicability to noise problems
that result from individual noise events or individual noise sources on adjacent properties such as am-plified
sound, mechanical equipment, dogs barking, or other common community noise sources. They
should be used together with additional information about the noise sensitivity of specific activities
and the characteristics of individual noise sources to develop regulations which apply to such noise
events. The Noise Ordinance is the appropriate place for establishment of such standards.
Because the standards are based on a single number that is intended to represent all aspects of the
noise environment, they may also need to be supplemented by special studies or special standards in
unusual or unique situations. Such special studies or standards are appropriate where the noise envi-ronment
includes unique conditions such as impact noise, noise with a high percentage of pure tones,
noise that occurs only or primarily at night, amplified sound including music and voice, or alarms and
sirens. Such noise problems tend to be focused on particular locations or situations, and are less an
issue when planning the overall arrangement of land uses in the General Plan.
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Figure 1. Standards for Land Use Compatibility with Urban Noise
Environments
55 60 65 70 75 80 85
Community Noise
Equivalent Level ( CNEL)
or Day- Night Level ( Ldn), dB
Residential- Low- Density Single-
Family, Duplex, Mobile Homes
Residential- Multi- Family
Commercial- Motels, Hotels,
Transient Lodging
Amphitheaters, Concert Hall,
Auditorium, Meeting Hall
Golf Courses, Riding Stables,
Water Rec., Cemeteries
Industrial, Manufacturing
Utilities, Agriculture
Office Buildings, Business,
Commercial and Professional
Schools, Libraries, Churches,
Hospitals, Nursing Homes
Land Use Category
Sports Arenas, Outdoor
Spectator Sports
Source: Cotton/ Beland/ Associates, based on State of California and U. S. Department of Housing and Urban
Development standards and guidelines and U. S. Environmental Protection Agency, Report on Levels of
Environmental Noise Requisite to Protect the Public Health and Welfare with an Adequate Margin of Safety,
1974.
Clearly
Acceptable
Conditionally
Acceptable
Normally
Unacceptable
Clearly
Unacceptable
New construction or
development should
generally be discour-aged.
If new construc-tion
or development
does proceed, a de-tailed
analysis of noise
reduction requirements
must be made and
needed noise insulation
features included in
design.
New construction or
development should
generally not be
undertaken.
Relatively quiet suburban or
urban areas, no arterial
streets within 1 block, no
freeways within 1/ 4 mile.
Very noisy urban areas near
arterials, freeways or
airports.
Extremely noisy urban
areas adjacent to freeways
or under airport traffic
patterns. Hearing damage
with constant exposure
outdoors.
Most somewhat noisy
urban areas, near but not
directly adjacent to high
volumes of traffic.
55- 65 dB
Below 55 dB
Nature of the noise
environment where the
CNEL or Ldn level is:
65- 75 dB
75+ dB
The Community Noise Equivalent Level ( CNEL) and Day- Night Noise Level ( Ldn) are measures of the 24- hour
noise environment. They represent the constant A- weighted noise level that would be measured if all the sound
energy received over the day were averaged. In order to account for the greater sensitivity of people to noise at
night, the CNEL weighting includes a 5- decibel penalty on noise between 7: 00 p. m. and 10: 00 p. m. and a
10- decibel penalty on noise between 10: 00 p. m. and 7: 00 a. m. of the next day. The Ldn includes only the
10- decibel weighting for late- night noise events. For practical purposes, the two measures are equivalent for
typical urban noise environments.
The noise environment
is suitable for this use.
Normally
Acceptable
Noise may be con-sidered
a problem by
some people, but normal
building construction will
usually provide ade-quate
protection of
interior spaces.
New construction or
development should be
undertaken only after a
detailed analysis of
noise reduction require-ments
is made and
needed noise insulation
features included in
design. Conventional
construction, but with
closed windows and
fresh air supply or air
conditioning, will nor-mally
suffice.
Playgrounds,
Neighborhood Parks
All categories: These guidelines
assume typical urban noise
environments and typical activities
associated with these land uses.
For unique noise- sensitive activi-ties,
unusual noise conditions, or
for individuals unusually sensitive
to noise, special conditions may
apply at any average noise level.
Thousand Oaks General Plan
Noise Element
14
1.4. Existing and Potential Future Noise Problems in Thousand Oaks
This section describes existing noise sources in the City that have the potential to result in noise con-flicts
with existing or proposed land uses.
Noise sources and the extent of noise impacts were determined based on community comments at
Noise Element workshops, noise monitoring at various points throughout the City, and computer mod-eling
of freeway and arterial noise.
1.4.1. Community Noise Concerns
Table 4 on page 17 summarizes the issues raised at community meetings held during the development
of the Noise Element. Although a number of noise sources and noise problems were identified in the
workshops, arterial roadway and freeway noise was by far the greatest concern of workshop partici-pants,
and occupied most of workshop discussion time. Retail area noise such as auto repair work and
retail delivery noise at specific locations was the second source in terms of number of people com-menting
and commonality of concern.
Other noise problems identified were largely isolated incidents or comments by only one workshop
participant, showing that the City has been successful in avoiding noise problems through appropriate
planning of land uses.
1.4.2. Community Noise Survey
A community noise survey was conducted in September, 1998 to identify existing conditions of the
noise environment throughout the City. The detailed report of this survey is available separately from
the City1. Forty- two individual monitor sites were selected for noise measurements. Monitor sites
were selected considering the following criteria:
At least some monitor sites used in the 1987 Noise Element should be monitored for comparison.
Wide geographic coverage of the City should be provided, including both noisy and quiet areas, so the
full range of the noise environment in the City can be identified.
Monitoring should include sites reflecting known existing problems such as arterial roadway noise in
residential areas, freeway noise, noise from retail and repair facilities, and noise from industrial plants.
Of the 42 sites, 12 sites were monitored for a 24- hour period. At the remainder of the sites, a sample
period of 15 minutes was used to identify typical conditions of the noise environment and to estimate
24- hour CNEL based on the field measurements for the sample period.
At each site, the maximum, various statistical noise levels ( L10, L25, L50 and L90) and the equivalent noise
level or energy- average noise level ( Leq) were calculated based on the measurement history at the site.
For sites monitored for 24 hours, the CNEL was calculated based on the actual hourly Leq for each hour.
For sites with 15- minute sample measurements, CNEL was estimated based on Leq + 2 decibels, a typi-cal
value based on the 24- hour measurements.
Figure 2 on page 15 shows the noise levels recorded at each of these monitor sites. In addition, the
figure shows noise levels measured in a study conducted in the same year for the Dos Vientos devel-opment
project, and noise levels recorded in monitoring conducted for the 1987 Noise Element.
1 Gordon Bricken & Associates, Results of the Community Noise Measurements for the City of Thousand Oaks,
October 12, 1998.
Thousand Oaks General Plan
Noise Element
15
No unique or unusual noise problem in specific locations was identified in the survey. The survey con-firmed
the overriding importance of motor vehicle noise in defining the noise environment throughout
the City.
Thousand Oaks General Plan
Noise Element
16
Figure 2 table – summary of noise monitor data – key to Fig 2 monitor sites
Thousand Oaks General Plan
Noise Element
17
Figure 2. Community Noise Monitoring Summary
( front of 11 x 17 foldout)
Thousand Oaks General Plan
Noise Element
18
Community noise monitoring summary
Back of 11 x 17 foldout
Thousand Oaks General Plan
Noise Element
19
Table 4. Noise Problems Identified at Public Meetings
Auto repair, pneumatic tools, tires, alarms
Delivery trucks
Leaf blowers, trash trucks
Freeway noise – can’t use hearing aid in back yard
Problems selling house because of freeway noise
Completion of 23 freeway made noise go on all night
Lynn Road traffic – 6,000 vehicles per day when arrived, now 26,000
High speeds on arterials – posted for 45, travel at 55
Widening of 23 will increase noise levels
Vibration from trucks
Air pollution from trucks
Lynn Road – used to be like a river, now like a waterfall
Motorcycles
Can’t use park by 101 freeway for softball because too noisy
Appraiser took $ 20,000 off value compared to comparables because of
noise
Parks – Oak Meadows, Conejo Lake Park, too noisy to read
Dogs barking – surrounded by dogs. People go to work, let dogs out, dogs
bark all day
Traffic – Thames Street – people use as a shortcut – Hendrix- Dover
Northwood – can’t hear TV in bedroom without window closed
EIRs – each project treats noise as miniscule – but all add up
Dos Vientos project will increase noise.
SUVs make more noise – big tires
On 23 and 101 – midnight -- early A. M. lots of 18- wheel trucks
California Lutheran – 1,000 parking spaces
Source: Comments at Noise Element public workshop April 29, 1998
Thousand Oaks General Plan
Noise Element
20
Traffic Noise
Traffic noise on arterial streets and freeways was identified as the most important noise problem in the
City by residents in community workshops. This perception is validated by both community noise sur-veys
and computer modeling of traffic noise.
Noise levels throughout the City cannot be monitored to identify the impact of traffic noise in detail.
Instead, computer modeling is used to estimate traffic noise levels based on the number of vehicles on
each roadway, the mix of vehicle types, percentage of vehicles using the roadway in the daytime, eve-ning
and nighttime hours, vehicle speed, and roadway configuration.
Aircraft Noise
While aircraft noise contributes to overall noise exposure in Thousand Oaks, aircraft noise is a minor
problem and an occasional irritant compared to traffic noise. There are only two aircraft noise issues
relevant to planning decisions in the City based on current and probable future operations. These two
issues are helicopter noise near hospital helipads, and the possibility of future helicopter noise if air
taxi service using helicopters is reinstituted at any local airports.
Commercial Air Traffic
While Thousand Oaks is beneath flight paths for approaches and departures from Los Angeles Interna-tional
Airport and Burbank Airport, its distance from these facilities means that aircraft are normally at
relatively high altitude and are widely dispersed, resulting in no substantial noise impact when com-pared
to background traffic noise. Such overflights were mentioned in public meetings but are not
considered a significant problem.
Private Fixed- wing Aircraft
Other airports that result in air traffic over Thousand Oaks include Oxnard, Camarillo, Santa Monica,
and Van Nuys Airports. Small private aircraft also result in noise events that contribute to overall noise
exposure in Thousand Oaks, but the contribution of these events to overall noise exposure is negligi-ble.
Helicopters
The Federal Aviation Administration has established freeway corridors as official helicopter routes for
travel throughout Southern California. While helicopters often use freeways as routes through Thou-sand
Oaks, the helicopter traffic volume is sufficiently low and altitudes are typically sufficiently high
that no substantial helicopter noise impact exists in comparison to the freeway traffic noise. Helicop-ters
also occasionally use helistops at hospitals for emergencies, at financial institutions for transpor-tation
of checks for clearing, and at public safety facilities for police helicopter operations. Only hospi-tal
helicopter flights were mentioned in community meetings as a potential noise problem. Helicopter
operations produce relatively high peak noise levels at nearby residences because they operate so close
to the ground and close to residential areas near hospitals.
Construction Noise
Construction noise typically involves the loudest common urban noise events. Construction equip-ment
involves large diesel engines, operating at high power to move heavy loads. It involves extensive
use of power and air tools, impact noise from hammering and use of explosive drivers for masonry
nails and anchors.
Construction activity is temporary at any given location, but can be substantially disruptive to adjacent
uses during the construction period. Construction results from both private land development activity,
and from public agency activity to construct utiities, streets and public buildings. The City currently
regulates the hours of construction activity to limit impact.
Mechanical Equipment Noise.
Mechanical equipment is used extensively in buildings to provide heating, cooling, air circulation and
water supply. Mechanical equipment that produces noise includes motors, pumps and fans. Fre-
Thousand Oaks General Plan
Noise Element
21
quently, this equipment includes components of pure tone noise from the rotational frequency of mo-tors.
Although noise levels are generally low from these sources at nearby properties, the fact that
such sources may operate continuously and may include pure tones that make them audible at a sub-stantial
distance makes them a potentially important noise source.
Portable Power Equipment.
Portable power equipment includes devices such as leaf blowers, lawn mowers, portable generators,
electric saws and drills, and other similar equipment. The noise source may result from the motor,
from the working surface of the tool on the work piece, from aerodynamic noise of blowers and fans, or
a combination of these sources. Portable power equipment is ubiquitous in the modern city, and can
produce very high noise levels at the location of the work.
Animals.
Animals including farm animals, dogs and cats have the potential to be an annoying noise source.
Noise impact of domestic animals is commonly a matter of individual property owners and is regulated
through animal control regulations which require owners to control noisy animals.
Amplified Sound.
Amplified sound includes noise from personal or home audio equipment, automotive audio equipment,
loudspeakers on sound trucks or in fixed installations used for paging, and amplified sound used for
music or theatrical performances. Because this sound typically includes music or speech, it is poten-tially
more detectable and more annoying than other sounds of the same noise level.
Horns, Bells and Sirens
Sound from horns, alarms, bells and sirens used by emergency equipment, trains or standard motor
vehicles may occur at any location in the City, and may be particularly disruptive to activities because
their purpose is to get people’s attention.
People
People talking, shouting, clapping, or stamping feet can create substantial noise levels, particularly if a
large number of people is involved. This source of noise is of particular concern at private parties, or
places of assembly such as entertainment facilities. Most complaints of people as a noise source re-sult
from noise of groups of people at night.
The nature and extent of each of the more significant noise problems identified in Thousand Oaks is
further detailed below.
1.4.3. Motor Vehicle Noise Impact
As a result of our dependence on motor vehicles, the predominant noise source in a city is typically
roadway traffic. In Thousand Oaks, traffic far outweighs all other noise sources in terms of the number
of people and residential units exposed to noise exceeding “ normally acceptable” noise levels. In
community workshops held to identify noise problems in the City, noise from freeways and arterial
streets was mentioned almost exclusively. Concern was particularly expressed over use of arterial
streets as freeway bypasses when freeways are congested. In addition, the growth of outlying areas of
the City which will put additional through traffic on existing arterials that pass through residential ar-eas
was commonly mentioned.
Vehicle noise levels vary depending on type of vehicle, engine size, speed, tires, roadway grade, pave-ment,
and other factors.
Figure 3 on page 23 shows an estimate of existing traffic noise levels in the City. Potential noise im-pacts
were estimated using the Federal Highway Administration’s Highway Traffic Noise Prediction
Model. In locations where major barriers or terrain effects would be expected to result in reduced noise
levels compared to those estimated by computer modeling, freeway noise contours are shaded. This
Thousand Oaks General Plan
Noise Element
22
analysis does not consider in detail the effect of noise barriers and terrain, or the barrier effect of other
buildings, on the width of the noise contours. However, it does provide an indication of the extent of
potential noise impact of traffic for a site with direct line- of- sight exposure to a substantial segment
of the roadway. The actual noise levels that would be measured at a given location depend strongly on
such factors as small local variations in topography, and the presence of barrier walls and buildings
between the roadway and the measurement point. Therefore, the noise levels in this figure should only
be considered an approximation of the maximum potential sound levels and their lateral limits extend-ing
beyond the edge of the pavement and an indication of where additional analysis may be appropri-ate.
A detailed noise monitoring survey or computer modeling that considers the details of noise path
conditions at each point in the City is not feasible.
For freeway noise impact areas, the map gives an indication of where terrain and barriers are likely to
provide a substantial reduction in noise level compared to the model prediction for unshielded sites.
Either an effective noise barrier wall or a row of intervening structures will typically provide a minimum
of 5 decibels and often 10 or more decibels of noise reduction. Thus, field conditions will often limit
the lateral extent of the noise contours if measured in the field.
Table 5 on page 21 provides an estimate of the area of land within the noise contours of Figures 3 and
4. As indicated above, this table indicates the area exposed to these levels assuming that no barriers
or other structures exist between the noise source and receiver. The table also includes the areas
within the public right- of- way, which may be as much as half of the area within the 65 dB CNEL noise
contours for arterial roadways. The right- of- way area is a much smaller percentage of the 60 dB CNEL
noise impact area for arterial roadways. It is also a very small percentage of the noise impact area for
freeways.
The threshold of adverse impact of noise on residential uses is approximately 55 dB CNEL. Because ter-rain,
existing development and other factors make the location of the 55 dB CNEL contour nearly totally
dependent on field conditions, computer models used to estimate the location of the 55 dB CNEL con-tour
may provide misleading results. Therefore the 55 dB CNEL contour was not calculated and is not
illustrated on the figures.
Thousand Oaks General Plan
Noise Element
23
Table 5. Existing and Proposed Land Use in Traffic Noise Impact Areas
General Plan
LandUseCategory 60- 65 dB > 65 dB Total 60- 65 dB > 65 dB Total 60- 65 dB > 65 dB Total
Residential
Residentially developable 34.6 26.7 61.4 41.0 42.3 83.3 6.4 15.6 22.0
Very Low Density 529.3 342.0 871.3 581.1 425.5 1,006.6 51.8 83.5 135.3
Low Density 1,759.5 1,173.0 2,932.5 2,042.8 1,482.8 3,525.6 283.3 309.8 593.1
Medium Density 616.0 516.9 1,132.9 651.6 625.1 1,276.7 35.6 108.2 143.8
High Density 214.2 151.8 366.0 208.9 192.3 401.2 ( 5.3) 40.5 35.2
Total Residential 3,153.6 2,210.5 5,364.1 3,525.4 2,768.0 6,293.5 371.8 557.6 929.3
Nonresidential
Commercial 414.6 1,195.5 1,610.1 337.9 1,322.7 1,660.6 ( 76.8) 127.2 50.5
Commercial/ Residential 22.3 2.2 24.4 27.7 2.8 30.6 5.5 0.6 6.1
Industrial 328.0 453.4 781.4 316.1 529.8 845.9 ( 11.9) 76.4 64.5
Institutional 65.7 54.5 120.2 76.7 68.1 144.8 11.0 13.6 24.5
Elementary School 38.8 7.0 45.8 66.0 8.9 74.8 27.1 1.9 29.0
Intermediate School 12.8 6.2 19.0 19.4 7.7 27.1 6.6 1.5 8.1
High School 29.3 15.8 45.1 48.5 19.4 67.8 19.2 3.6 22.8
Park, Golf, Open Space 909.3 782.7 1,692.1 1,089.8 920.9 2,010.7 180.5 138.2 318.7
Proposed Park and Recreational Area 1.4 1.1 2.4 14.0 12.1 26.1 12.6 11.1 23.7
Lake 2.3 1.3 3.6 3.6 1.8 5.3 1.3 0.4 1.7
Reserve 82.3 70.1 152.4 94.5 96.9 191.4 12.3 26.8 39.1
Undefined - 19.8 19.8 - 19.8 19.8 - - -
Undevelopable 166.5 183.8 350.4 184.7 224.5 409.3 18.2 40.7 58.9
Total Nonresidential 2,073.2 2,793.3 4,866.5 2,278.8 3,235.2 5,514.0 205.6 441.9 647.5
Total Al Uses 5,226.9 5,003.8 10,230.6 5,804.3 6,003.2 11,807.5 577.4 999.5 1,576.8
% of total City land area: 13.5% 13.0% 26.5% 15.0% 15.5% 30.6% 1.5% 2.6% 4.1%
Source: Cotton/ Beland/ Associates, based on analysis of noise contours of Figures 3 and 4, excluding areas where terrain or exisitng barriers would
be expected to substantially reduce noise levels.
Totals may not add in last decimal place due to rounding throughout table.
Land Area in Acres by Noise Level
Existing Projected Change from Existing
Thousand Oaks General Plan
Noise Element
24
Thousand Oaks General Plan
Noise Element
25
Figure 3. Existing Freeway and Arterial Street Traffic Noise Levels.
( 11 x 17 foldout, front)
Thousand Oaks General Plan
Noise Element
26
Figure 3, continued
11 x 17 foldout, back
Thousand Oaks General Plan
Noise Element
27
Figure 4. Projected Future Freeway and Arterial Street Noise Levels.
( 11 x 17 foldout, front)
Thousand Oaks General Plan
Noise Element
28
Figure 4, continued
11 x 17 foldout, back
.
Thousand Oaks General Plan
Noise Element
Public Review Draft 29 April 10, 2000
2. Goals and Objectives
The City of Thousand Oaks seeks to maintain a standard of high environmental quality for all its
residents. Thousand Oaks is predominately a residential community. A quiet environment is im-portant
to the quality of life in a residential area. The goals of the Noise Element are directed pri-marily
at maintaining and improving the environment of residential areas and other noise-sensitive
land uses by minimizing the adverse impacts of noise.
The Noise Element is only one element of the City’s General Plan. In some specific situations, the
goals, objectives, policies or programs of the noise element may conflict with other parts of the
General Plan. In such cases, the City may determine that other objectives take higher priority, or
that some balance is needed between the competing objectives.
Goal N- 1. Achieve and maintain an environment in which noise- sensitive uses are not disturbed by noise that ex-ceeds
exposure guidelines established in this Noise Element.
This goal reflects the need to maintain basic environmental standards for quiet in residential areas
and other noise- sensitive areas of the City. Where noise levels already exceed these standards,
efforts to reduce noise levels should be directed at the source, and by measures to protect sensi-tive
uses through sound insulation or noise barriers. Where noise conflicts cannot be eliminated
in this way, in concept the conflict can be resolved by encouraging conversion of the noise-sensitive
uses to uses which are less noise- sensitive. However, no substantial area in Thousand
Oaks was identified where such land use conversion is justified based on the existing noise envi-ronment.
Such conversion could have other land use policy implications, and is normally consid-ered
only in severe noise problem cases where no alternatives exist.
Policy N1- 1. Land Use Compatibility for Noise. In establishing the pattern of land uses and
setting standards for development within land use categories, the City will consider the need to
minimize the potential for conflicts between noise- sensitive land uses and activities and land uses
that are normally expected to generate noise.
Policy N1- 2. Reduction of Existing Noise Conflicts at the Source. Recognizing that
reduction of noise at the source is normally the most efficient strategy for reducing noise
conflicts, and results in the greatest benefit in reducing overall noise exposure, the City will
emphasize reducing noise levels at the source as the primary or preferred strategy for reducing
potential conflicts.
Policy N1- 3. Reduction of Existing Noise Conflicts by Other Means. Where it is not the
most feasible measure to reduce noise conflicts at the source, the City will work to provide other
protection for noise- sensitive land uses in areas exposed to noise that exceeds or is expected to
exceed the noise guidelines for noise- sensitive land uses adopted in this Noise Element.
Policy N1- 4. Prevention of Future Noise Conflicts. The City will strive to avoid future
noise conflicts between land uses and noise sources or activities that would exceed the noise
guidelines for noise- sensitive land uses adopted in this Noise Element.
Policy N1- 5. Regulation of Nuisance Noise Sources. The City will maintain and actively
enforce a noise ordinance which addresses the problems that may result from time to time from
people’s activities, use of mechanical equipment, amplified sound, and other sources of potential
noise conflicts between users of property in the City. In regulating such noise sources, the City
may consider such factors as noise level, frequency distribution of sound, duration and number of
noise events, tonal content, information content such as music or human speech, time of day, and
any other appropriate factors found to relate to human annoyance or interference with human ac-tivities.
Thousand Oaks General Plan
Noise Element
April 10, 2000 30 Public Review Draft
Policy N1- 6. Monitoring of the Noise Environment. The City will regularly evaluate the
noise environment to ensure that the objective of minimizing reducing noise conflicts is being
achieved. As a general guideline, a comprehensive review of community noise levels may be con-ducted
approximately every 10 years.
Goal N- 2. Preserve quiet and diminish existing noise levels in areas of noise- sensitive uses to the extent reason-able
and feasible while permitting development in accordance with the Land Use and Circulation Elements of the
General Plan.
This goal reflects the fact that even in areas that currently meet noise standards, the quality of the
environment is in general improved by reducing ambient noise levels from urban activities, and is
degraded if ambient noise levels increase. Since people have varying sensitivity to noise, providing
choices including the choice of living in areas where existing quiet will be preserved is a matter of
policy.
Although preserving quiet is an important objective, locations within the City will experience un-avoidable
increases in ambient noise levels as a result of development or transportation system
improvements in accordance with the Land Use and Circulation Element policies of the General
Plan. The City does not intend to limit such development in order to achieve this goal.
Policy N - 2.1. Consider Impact of Noise Increases in Quiet Areas. In evaluating projects
for significant adverse environmental effects under the California Environmental Quality Act, the
City will consider substantial increases in community noise level to be a potentially significant
effect even if these increases do not result in a violation of the City’s guidelines for normally ac-ceptable
noise levels for noise- sensitive land uses.
Thousand Oaks General Plan
Noise Element
31
3. Solving Noise Problems
This section of the Noise Element discusses the nature of the most important noise problems facing
the City, and identifies ways to address these problems.
Section 3.1 discusses the nature of noise problems and how various approaches can be used to ad-dress
them. It examines the appropriateness and need for City action to address each noise issue. This
analysis provides the basis for the City’s comprehensive noise abatement program outlined in Chapter
4.
Appendix B provides a list of noise control strategies identified by the California Office of Noise Con-trol
in its advisory Noise Element Guidelines. The discussion below and in Chapter 4 describing the
City’s noise abatement programs includes those strategies most applicable or important in Thousand
Oaks.
3.1. Noise Control Strategies
A noise conflict situation involves a noise source, a path through which the noise travels, and a noise-sensitive
receiver. Depending on the nature of the situation, the problem may be addressed at any of
these three points.
Table 6 on page 33 is an outline of noise abatement strategies for motor vehicle noise that illustrates
how noise conflicts can be reduced by acting at each of these points in the system.
Table 7 on page 34 is a summary of various noise control strategies for dealing with a variety of noise
sources. This table summarizes the effectiveness of each strategy, its limitations and costs, and other
considerations that may affect its implementation.
3.1.1. Noise Control at the Noise Source
Because a noise source may affect many different receivers, it is generally most efficient to deal with
noise problems at the source. The objective of noise control at the source is to reduce the total
amount of sound energy which reaches the environment from the noise source, or to change other as-pects
of the noise source which affect human response.
Noise sources produce sound energy and transmit it to the environment in a number of ways. These
include direct excitation of vibrations in air ( fans, loudspeakers, internal combustion engine exhaust,
vibrating engine parts, air compressors, pumps), friction of metal parts ( motors, fans, drilling), and
pressure waves from striking of solid objects ( sawing, hammering, banging, drilling, tires on roadway).
The amount of sound energy generally increases with speed, force, and mass of air movement.
Sound energy can be reduced by modifying the system that creates the noise to produce a lower noise
level, to reduce the amount of time the source generates noise, and/ or to change the time of day to a
less- sensitive time period. Sound energy emitted to the environment may be reduced by placing
sound absorbing material around the source or along the path by which sound reaches the general en-vironment
from the source. For a noise source made up of many different sources, such as urban
traffic, the noise level may be reduced by reducing the number of individual noise events, or by reduc-ing
the noise level of each individual event.
3.1.2. Reducing Motor Vehicle Noise at the Noise Source
Table 6 on page 33 is an outline illustrating how motor vehicle noise can be controlled at the noise
source, in the noise path, or at the noise receiver.
Traffic noise levels from a given roadway increase with the number of vehicles, the average noise level
of each vehicle, average speed, the percentage of trucks in the fleet mix, and the percentage of vehi-
Thousand Oaks General Plan
Noise Element
32
cles traveling at night. Other factors such as the number of vehicles violating muffler laws, squealing
tires, occasional speeding, and vehicles with loud music systems, may increase annoyance without
substantially affecting the total noise level. The smoothness of the pavement surface, and whether a
sound- deadening treatment such as rubberized asphalt has been applied, can also affect noise level.
3.1.2.1. Noise Levels of Individual Vehicles
Local regulation of noise from automobiles is preempted by state law in California. California regu-lates
the maximum noise level produced by mufflers, requires maintenance of mufflers and exhaust
systems, and regulates the maximum noise produced by auto sound systems. Local agencies enforce
these regulations, which are found in the California Vehicle Code. While enforcement of regulations
can be effective in eliminating the most annoying individual vehicles, this enforcement has little im-pact
on overall community noise exposure, because almost all vehicles comply with the state regula-tions.
The State of California regulates the maximum noise level produced by the muffler system of newly
manufactured vehicles ( see Appendix A). However, the maximum permitted noise level is substantially
greater than the average noise level of typical vehicles, and the regulation has little effect on vehicle
noise levels. When first adopted, the regulations prohibited aftermarket exhaust systems which ex-ceeded
original equipment noise levels; however, a few years after introduction this requirement was
removed. Aftermarket exhaust systems are now permitted to be sold if they do not exceed the maxi-mum
permitted noise level.
While heavier cars require larger engines than small cars, and their larger tires and greater weight
would be expected to result in more tire noise, their large size also permits greater sound insulation
around the engine compartment. Large cars, including sport utility vehicles, are in general not noisier
than smaller cars, although certain tread patterns can result in higher noise levels. At freeway speeds,
tire noise is the dominant noise source from cars.
City efforts to reduce the typical noise of individual vehicles are limited to enforcement of vehicle
code noise levels and advocacy of lower noise levels for newly manufactured vehicles and aftermarket
exhaust systems.
3.1.2.2. Vehicle Speed.
Figure 5 on page 31 illustrates the effect of vehicle speed on noise level. In the discussion that fol-lows,
a standardized example of an arterial roadway is used to show the effect of various noise reduc-tion
strategies. This standardized example is a four- lane arterial roadway with 10,000 vehicles per
day. The fleet mix is 94% autos, 4% light trucks and 2% heavy trucks ( semi- trailer diesel trucks). The
time of day distribution is 70% day, 15% evening and 15% night, based on a survey of arterial roadway
data conducted in Los Angeles County by CBA staff.
Reducing vehicle speed on this sample arterial street with 10,000 vehicles per day from 45 mph to 35
mph would reduce the average noise level from a typical mix of traffic at 75 feet from the centerline of
the roadway from 67.3 dB CNEL to 65.0 dB CNEL, a reduction of 2.3 decibels. A reduction of 2.3 deci-bels
is equivalent to reducing the number of vehicles by approximately 42%, to 5,800 vehicles.
State law limits the ability of Cities to enforce speed limits which are lower than limits determined in a
survey of current traffic speeds unless specific safety considerations are involved. Reducing speeds
for noise abatement must therefore be accomplished by means other than setting the legal speed
limit, or through legislation permitting use of the speed limit for this purpose.
3.1.2.3. Number of Vehicles
Table 10 on page 61, following the Glossary, provides a convenient method of determining the impact
on total noise exposure of changes in the number of vehicles or other approximately identical noise
sources. Figure 5 shows that 10,000 vehicles at 45 mph result in a noise level of 67.2 dB CNEL at 75
feet from the centerline of the roadway. Reduction of the noise level by 3 decibels to 64.2 dB CNEL
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would require a reduction in traffic volume of 50%. To reduce the noise level by 10 decibels would
require a reduction in traffic to 1,000 vehicles, a reduction of 90%.
Because of the large change in traffic volume required to produce a substantial reduction in noise
level, reducing traffic volume is generally not a practical solution to arterial traffic noise problems. An
exception is if there is an alternate route that has substantially less noise- sensitive use, or is pro-tected
by barriers or distance from noise- sensitive land uses.
Figure 5. Noise as a Function of Vehicle Speed
This figure illustrates the effect of vehicle speed and the contribution of autos, medium trucks and
heavy trucks to daily average noise levels for an arterial street with a typical mix of vehicles and typi-cal
distribution by time of day.
Contribution to CNEL Value by Vehicle Type and Speed
10,000 Vehicles per Day, Typical Arterial Fleet Mix
50.0
55.0
60.0
65.0
70.0
75.0
25 30 35 40 45 50 55 60 65
Speed ( mi/ hr)
Noise Level, dB CNEL
at 75 feet from Centerline
Autos
Light Trucks
Heavy Trucks
All Vehicles
Assumptions:
Fleet mix: 94% autos, 4% light trucks, 2% heavy trucks
Time of day: 70% day, 15% evening, 15% night.
Less than 1% grade
Soft site
Caltrans noise model data by vehicle type.
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3.1.2.4 Development Density
A number of residents at public meetings on the Noise Element commented that reduction of the per-mitted
density of as yet undeveloped areas should be considered as a means of reducing noise.
Unless the reduction in density is substantial, noise reduction resulting from this strategy is relatively
small. Reductions in density do not proportionately reduce vehicle travel or noise, since lower density
in general results in a higher number of vehicle trips per dwelling unit, longer average trips and total
vehicle miles traveled, and higher vehicle speeds, all of which counteract the effect of reduction in
density.
An exception exists where the density reduction results in the elimination of certain areas from po-tential
development. Roadways directly serving these areas may have substantially less traffic and
resulting noise level than if the area were developed. Because most of Thousand Oaks is nearly built
to its potential development density under the General Plan, very little community noise benefit is to
be gained from reducing the potential development density of as yet undeveloped areas.
3.1.2.5. Fleet Mix.
Heavy diesel trucks have high noise levels compared to cars, particularly at low speed. Because en-gine
and exhaust noise is a higher percentage of truck noise than car noise, truck noise levels do not
rise with speed as much as automobile noise levels. Figure 5 on page 31 shows the difference in con-tribution
of autos and trucks to total vehicle noise exposure at different speeds. While the contribu-tion
of autos increases from 61.9 dB CNEL at 35 mph to 67.5 dB CNEL at 55 mph, a change of 5.6 dB,
the contribution of heavy trucks increases from 60.0 to 61.8 dB CNEL, a change of 1.8 dB.
Because trucks contribute more of the total noise exposure at low speeds, changing the number of
trucks as a percentage of the fleet has a greater impact at low speeds. The effect of reducing the per-centage
of trucks is also greater if the roadway has a high percentage of truck traffic.
For an arterial street that currently has a high percentage of truck traffic and a relatively low average
speed of 35 mph, changing the percentage of trucks from 5% to 2% would reduce the noise level at 75
feet from the centerline of the roadway from 66.6 dB CNEL to 65.0 dB CNEL, a reduction of 1.6 dB
CNEL. Reducing the percentage of trucks further from 2% to 0% would further reduce the noise level
from to 65.0 to 63.4 dB CNEL, a reduction of 1.6 dB. Reducing the percentage from 5% to 2% on a
roadway with a typical speed of 55 mph would reduce the noise level from 70.2 dB CNEL to 69.3 dB
CNEL, a change of only 0.9 dB. Thus, restricting truck use with the City’s ability to establish truck
routes with noise abatement in mind on local arterials and collector streets can be effective in reduc-ing
noise levels, but has greater impact at low speeds and for roadways that already have a high per-centage
of truck traffic.
3.1.2.6. Time of Day.
Reducing the percentage of vehicles that travel in the evening or at night could reduce the average
noise level. Elimination of all traffic between 10: 00 p. m. and 7: 00 a. m and distributing this traffic
proportionately over the remaining hours of the day would reduce the noise level of the sample arterial
roadway from 65.0 dB CNEL at 75 feet from the roadway to 61.3 dB CNEL, a reduction of 3.7 dB CNEL.
As a practical solution, this strategy has limited effectiveness because of the inability of local gov-ernment
to control people’s driving choices, and the fact of long commutes in a large metropolitan
region.
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Table 6. Outline of Potential Noise Abatement Strategies
I. Noise Source
A. Levels of individual vehicles
1. Quieter vehicles
a. Quieter tires.
b. Lighter vehicles ( providing adequate sound insulation is provided).
c. Improved muffler systems.
d. Control sound system volume.
2. Reduce number of vehicles violating exhaust system or noise standards
3. Reduce speed
4. Rubberized asphalt
B. Number of vehicles
1. Reduce number of vehicles on roadway
a. Reroute to other locations
b. Minimize total vehicle miles traveled
C. Fleet mix
1. Reduce percentage of trucks
D. Time of day
1. Reduce nighttime travel by all vehicles
2. Reduce nighttime travel by trucks
II. Noise Path Changes
A. Increase distance between source and receiver
B. Barriers between source and receiver
III. Noise Receiver Changes
A. Receiver location changes
1. Encourage compatible development in noise impact areas
2. Relocate existing incompatible uses
3. Prohibit incompatible uses in noise impact areas
B. Receiver sensitivity changes
1. Insulation of structures
a. Insulation requirements
b. Insulation retrofit programs for existing uses
2. Sound masking
3. Public relations
IV. Feedback and control mechanisms
A. Development fees based on noise impact
B. Regulation of noise sources
C. Provide information to buyers and builders
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Table 7. Noise Abatement Strategies: Costs, Effectiveness, Other Considera-tions
Noise Abatement Strategy Noise Reduction Costs Limitations, Comments, Other Considerations
Motor Vehicle Noise
Reduced noise levels of individ-ual
vehicles ( engine insulation,
mufflers, quiet tires)
2- 3 dB average over time as
older vehicles are retired from
the fleet
To a few hundred dol-lars
per vehicle over life
cycle
Likely to require federal action, City has little influence.
Increased fuel consumption for heavier vehicles.
Eliminate noise and muffler law
violators
Less than 1 dB average, can
reduce peaks from worst
offenders substantially
$ 5- 10,000 per year Requires training, equipment, allocation of police and attor-ney
time, signs and public relations program. Limited
ability to be there when worst offenders are causing noise
problems
Reduce arterial roadway speed 2 dB for reduction of auto
speed from 45 mph to 35 mph
Signage, enforcement Enforcement problems from legal requirements for setting
speed limits. May require state legislation.
Reduce truck percentage in fleet
mix
2 dB for reduction of heavy
trucks from 4% to 2% of fleet
Cost of establishing
truck routes
Likely to relocate trucks to other locations with similar noise
sensitivity.
Reduce nighttime travel 1 – 1.5 dB for cutting nighttime
volume in half ( 10 PM – 7 AM)
Likely to relocate nighttime traffic to another location. In-cludes
early morning commute hours.
Reduce number of vehicles on
roadways
1 dB for 20% reduction in
traffic, 3 dB for 50% reduction
in traffic, 5 dB for 68% reduc-tion
in traffic
Varies – signage,
neighborhood traffic
control ( barriers, traffic
calming), upgrade alter-nate
routes
Requires either demand reduction or availability of adjacent
routes for relocation of traffic. Requires substantial reduc-tion
in traffic ( 30- 40%) for meaningful reduction in noise
level. Ridesharing, HOV lanes.
Reduce density or intensity of
future development
Proportional to reduction in
traffic.
Increased infrastructure
per unit of use, lower
city revenues per unit of
area for some revenue
sources
Reduction in density results in less than proportional reduc-tion
in noise since additional travel per unit is required with
lower density, and higher average speeds are likely with
low- density development. May force development out to
greater distances, increasing through traffic with reductions
in locally generated traffic.
Reduce nighttime travel 3.7 dB with elimination of all
night travel for a typical fleet
mix.
Unknown Difficult to force this kind of driver choice.
Aircraft Noise
Ensure helicopters follow free-way
routes, particularly during
special VFR
To 1 dB CNEL for heavily
impacted areas
May require substantial
effort to address if a
problem occurs
FAA routes are recommended, difficult to influence FAA
Limit heliports to locations where
immediate access to acceptable
routes is possible
To 3- 5 dB CNEL for a resi-dence
that might be affected
by a large number of helicop-ter
operations
Nominal regulatory and
enforcement cost, appli-cant
covers CEQA
costs
Zoning for heliports, CEQA process. Not currently a
significant noise problem, though may be a nuisance near
hospital emergency heliports.
Minimize noise from approaches
and departures from LAX, Bur-bank,
Van Nuys, Oxnard and
Camarillo airports
No measurable impact on
CNEL since not likely to
affect CNEL, may reduce
peaks from overflights 3- 5 dB
May be difficult and
expensive to influence
FAA if a problem oc-curs.
Likely to move impact to another area which may com-plain.
Not currently a significant noise problem. Future
navigational systems may improve control.
Mechanical Equipment Noise ( pumps, fans, compressors, etc.)
Quantify noise limits in Noise
Ordinance. Limit noise level by
time of day, adjacent zoning
district
Localized benefit, little change
in CNEL. Limit to acceptable
levels, minimize interference
with adjacent activities
Nominal regulatory and
enforcement cost, re-duces
cost relative to
“ disturbance of the
peace” standards by
providing clear violation.
Review of Noise Ordinance part of Noise Element Update
program.
Require shielding around noise
sources
Noise limits define benefit.
Shielding may not change
Nominal regulatory and
enforcement cost
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Noise Abatement Strategy Noise Reduction Costs Limitations, Comments, Other Considerations
noise level
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Noise Abatement Strategy Noise Reduction Costs Limitations, Comments, Other Considerations
Nuisance Noise ( animals, people, deliveries, miscellaneous noise sources)
Limit hours of commercial deliv-eries
near residential areas.
Reduce nuisance noise during
most sensitive hours.
Nominal regulatory and
enforcement cost
“ Disturbance of the Peace” pro-visions
in Noise Ordinance
Existing City noise ordinance
includes provisions
Nominal regulatory and
enforcement cost
Difficult cases may require specific noise limits in ordi-nance.
Construction Noise
Prohibit night construction except
for emergencies
5- 7 dB average daily CNEL
during construction period
compared to 24- hour operation
Current City program.
Negligible regulatory
and enforcement costs
Substantially reduces complaints.
May reduce contractor flexibility for specific operations
( such as large concrete pours)
Increases duration of construction, reduces intensity but
increases duration of air quality and other impacts. In-creases
traffic congestion because operations are during
peak travel hours.
Limit number of pieces of heavy
excavation equipment
1- 3 dB average daily CNEL
and peak noise level, no
change in annual
Negligible regulatory
and enforcement costs
Increases construction and carrying costs for projects,
increases duration of construction, without reducing total
noise exposure over the year.
Truck haul routes away from
residential areas ( existing pro-gram)
1- 5 dB average daily CNEL
on roadways during construc-tion
period
Negligible regulatory
and enforcement costs
Moves noise to another location – requires availability of
alternate routes. May increase air pollution and travel time
if requires substantial detour, normally not significant
Require special quiet equipment
( such as compressors) within
500 feet of noise- sensitive areas
10 dB or more from quiet
compressors. Little impact on
CNEL because temporary
Moderately higher
equipment lease costs,
some impact on utility
construction costs
Equipment generally available, used for OSHA compli-ance
by many contractors.
Animals
Noise ordinance or animal control
ordinance to limit problems from
barking dogs, other animals
( existing program)
No substantial change in
CNEL. Reduces a significant
potential nuisance
Existing program. Con-tract
for animal control
Amplified Sound
Limit sound levels produced by
amplified sound used outdoors,
near noise- sensitive uses, re-quire
permits
No substantial change in
CNEL. Reduces a significant
potential nuisance.
Nominal additional city
cost to manage permit
process
May require use of pagers rather than outdoor paging for
some uses
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3.1.3. Noise Control in the Noise Path
Along the noise path, noise impact may be reduced by placing barriers between the source and the
receiver. Noise may also be reduced by increasing the length of the noise path by moving either the
source or receiver to a greater distance.
3.1.3.1. Barriers.
To be effective, barriers must obstruct the line of sight between the source and receiver. Noise reduc-tion
by barriers is a function of the ratio of the length of the noise path with the barrier to the noise
path without the barrier. This ratio is greatest when the barrier is close to either the source or re-ceiver,
and least when it is located at an equal distance between them.
Barriers are particularly effective at reducing noise from automobiles, which is created at high speeds
primarily by tires. Because this noise is created close to the roadway, barriers are very effective in re-ducing
this noise. An 8- foot to 12- foot barrier wall on a freeway can reduce noise by 10 decibels or
more compared to the case without the barrier. However, even a small break in a barrier can substan-tially
reduce its sound attenuation value. Substantially higher barriers are required to reduce truck
noise, much of which comes from the exhaust outlet at a height of 10 to 12 feet. To be most effec-tive,
barriers need to be high and continuous.
In some cases, barriers on one side of a roadway may slightly increase noise on the opposite side of
the roadway by reflecting noise back to the other side of the roadway. Because of the greater distance
and the fact that a substantial amount of such noise is absorbed in the noise path, this contribution to
noise levels is in general quite small compared to the benefit of barrier walls. However, in cases in
which it may be a problem, sound- absorbing barrier walls, or compensating barriers on the opposite
side of the roadway, may be considered.
Barriers are only practical and effective where access is not required to adjacent uses. For this reason,
subdivision design which avoids residential driveway access on arterial roadways is recommended.
3.1.3.2. Distance
Increasing the distance between the source and receiver is particularly effective at close distances
( less than 50 feet from the source, for example), where a small increase in distance can substantially
reduce noise levels. For a point source of noise, increasing the path distance typically reduces the
noise level by 6 decibels or more for each doubling of distance, depending on the characteristics of
the path over which sound travels. For a line source of noise such as a roadway, increasing the path
typically results in a 3 to 4.5- decibel reduction for each doubling of distance. At longer distances, the
additional distance needed for each decibel of noise reduction increases substantially, and a substan-tial
unusable area can result from using separation by distance as a noise attenuation strategy.
3.1.4. Noise Control at the Receiver
At the receiver, sound insulating material may be placed around the receiver, or masking noise may be
used to reduce the intrusiveness of the noise source. The receiver may be relocated to a location far-ther
from the source.
3.1.4.1. Sound Insulation.
Typical residential construction with no special attention to sound insulation typically results in 20 to
25 decibels of noise reduction between in outside and inside of the unit with windows closed. Sound
insulation can increase this sound reduction by up to 10 decibels. Achieving more than 35 decibels of
sound insulation in a residential unit is likely to involve unusually high costs.
Sound insulation at the receiver is particularly effective for unusually noise- sensitive uses ( such as
recording studios, or residences of people who are unusually sensitive to noise). It is also an appro-priate
strategy in cases in which a high noise level results from a wide variety of different noise
sources, making it difficult to reduce noise at the source.
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California law requires all new multiple- family residences to provide sound insulation from exterior
noise sources to maintain an interior noise level of 45 dB CNEL or lower in all habitable rooms. The
City finds that in order to preserve housing values and protect the health and welfare of residents, this
standard should also apply to new single- family residences.
As a strategy for reducing noise impact in residential areas exposed to high noise levels, sound insu-lation
is more effective for multi- family residences than for single- family detached housing. Occu-pants
of single- family homes generally place substantial value on outdoor living. Outdoor living ar-eas
cannot be protected by sound insulation.
3.1.4.2. Sound Insulation Retrofit of Existing Residences
Sound insulation retrofit of existing residences is an expensive method of achieving acceptable noise
levels for interior living areas. However, in cases in which the noise source cannot be effectively con-trolled,
such as on existing residential streets with high traffic volumes, it may be the only method
available.
Sound insulation retrofit for aircraft noise has been studied extensively in pilot programs for Los An-geles
International Airport and other locations. The effectiveness of retrofit is highly dependent on
the quality of construction, since small holes and gaps can allow substantial leakage of sound energy
around openings.
Sound insulation retrofit for motor vehicle noise sources can be less expensive than for airport noise,
since normally only one or two building faces are affected, with the other faces protected by the
structure itself, and insulation of the ceiling and roof is less important.
In a pilot study conducted for Los Angeles International Airport in 1982, Wyle Laboratories identified
strategies and costs of meeting the 45 dB CNEL interior sound level for a variety of types of residential
structures exposed to aircraft noise. 2 The discussion of sound insulation below is based on that
study.
In insulating houses against exterior noise, modifications must be made considering the three paths
by which sound enters the structure:
1. Air filtration paths ( gaps and cracks),
2. Small wall elements ( windows and doors), and
3. Main wall elements ( walls, roofs and floors).
Air Filtration Paths
Air filtration paths are the small gaps and cracks that normally exist around doors and windows. Even
if the noise reduction effectiveness of the walls is high, that effectiveness will be lost if there are are
air filtration gaps or windows and doors with poor acoustic performance.
The improvement in noise reduction that can be obtained merely by treating the leakage paths without
modifying the windows, doors or other building elements has been shown to be on the order of 2 dB,
but could be as high as 5 dB depending on the condition of weatherstripping and seals. Thus the first
step in increasing the noise reduction of residences is to seal all infiltration cracks using weather-stripping,
non- hardening caulking, and door threshold seals. If the sealing of cracks and leaks does
not achieve the desidred interior levels, then modifications of the building elements are required.
2 Wyle Laboratories, Residential Sound Insulation Retrofit Cost- Effectiveness Analysis, Wyle Research
Report WR- 82- 16, May, 1982.
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Small Wall Elements
Since small wall elements such as windows and doors usually have noise reduction values less than
that of the surrounding wall, they must usually be modified in the second stage of soundproofing.
This modification should upgrade these elements to a sound reduction value close to that of the sur-rounding
wall. This is achieved by replacement with improved elements, and can result in noise re-duction
increases of up to 10 dB. One basic small element modification is the installation of secon-dary
glazing for doors and windows ( conventional storm windows and doors are the most cost-effective
form of openable secondary glazing). This modification can provide a substantial increase in
door and window noise reduction values, but must remain in place if the benefits are to be realized
year- round. In this stage of soundproofing, acoustic baffles in air vents, chimneys, and kitchen ducts
are generally necessary.
Main Wall Elements
The final stage of sound insulation is the modification of the major wall elements. This stage of sound
insulation is substantially more expensive than the previous two steps, and requires careful custom
evaluation and design of the wall, floor and roof.
Ventilation Requirements
Air conditioning is required to achieve the sound reduction benefits of the modifications discussed,
since all value of eliminating air filtration gaps and double- glazing of windows and doors are lost if
doors or windows are left open for ventilation. The climate of Thousand Oaks requires air condition-ing
for year- round comfort with windows closed. Thus the cost of air conditioning must be consid-ered
as part of the sound insulation cost for any residence that is not currently provided with air con-ditioning.
Window air conditioners are generally not satisfactory for this purpose since they provide
an additional path for sound to enter the unit.
Costs of Sound Insulation Retrofit
The Wyle Laboratories study provided cost estimates, in 1981 dollars, for sound insulation retrofit of
the structures common in the study area. Because these costs are estimates for aircraft noise, which
is less directional in its impact on residences than motor vehicle noise, costs for insulation from vehi-cle
noise could be less. 1981 cost estimates were multiplied by 2.5 to provide a 1999 dollar estimate
of costs for Thousand Oaks. These estimates should be considered a general and comparative guide
only. The actual costs of such retrofit vary greatly with the nature of the individual structure being
retrofitted.
Table 8. Sound Insulation Retrofit Cost Estimates
Cost per Square Foot to Increase Noise Reduction to:
Dwelling Unit Type 20 dB 22.5 dB 25 dB 27.5 dB 30 dB 32.5 dB
Single- family, One- Story 0.20 1.35 2.25 5.25 9.00 12.00
Multi- family, Lower Floor, Interior Unit 0.03 0.20 0.35 0.80 1.40 2.00
Multi- family, Lower Floor, End Unit 0.10 0.40 0.55 1.70 3.25 4.25
Multi- Family, Top Floor, Interior Unit 0.03 0.25 0.50 1.60 2.75 3.75
Multi- Family, Top Floor, End Unit 0.12 0.60 1.00 3.00 5.00 7.00
Source: Cotton/ Beland/ Associates, based on information from Wyle Laboratories, Residential Sound
Insulation Retrofit Cost- Effectiveness Analysis, WR 82- 16, 1982. Standard noise reduction for typical
residential units is approximately 15 to 20 dB. Costs are adjusted from 1981 estimates by multiplying
by approximately 2.5. Costs do not include costs of architectural drawings, permits, minor repairs to
Thousand Oaks General Plan
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42
existing structures, and contractors contingency, which may add approximately 30% to the above
costs.
3.1.3.3. Sound Insulation for New Construction
The cost of sound insulation for new construction is substantially less than that for retrofit to existing
structures, since the cost can be incorporated in the original plans and specifications for the struc-ture,
and removal of existing materials and custom fitting to existing conditions is not required. Be-cause
of the thermal insulation requirements of the current California building code, newly con-structed
residential buildings typically include double- pane windows and good weather sealing
around window and door openings.
3.1.3.4. Sound Masking
Sound masking is the camouflaging of background noise events by addition of “ white noise,” music,
or another sound source. Such masking can be effective in quiet environments where small noise
events can cause distractions. It is less effective when the masking sound level needs to be high ( 55
dB or greater) to mask noise events, and when the interrupting noise events are substantially louder
than the background noise level.
Sound masking may be effective for individuals that are exceptionally sensitive to noise interruptions
at night. Sound masking can mask low- level noise events, such as from distant traffic, preventing
sleep interruptions.
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4. Quiet City Program
This chapter outlines the City’s proposed program to achieve the goals and objectives of the Noise
Element.
Some of the programs outlined below involve substantial cost, require substantial staff time, or re-quire
additional studies or regulations. All such programs compete for public funds and the resources
of the City, and are subject to the City’s regular annual budgeting procedures in which the City sets
priorities among competing objectives. The Noise Element does not make these programs mandatory,
but provides a list and description of programs that the City may consider to reduce noise.
4.1. Land Use Planning Standards
Objective. Establish and maintain standards for acceptable noise levels for various noise- sensitive
land uses in the City so that the potential for noise conflicts can be identified and avoided in major
land use and transportation planning decisions.
Program. Utilize the land use compatibility standards of Figure 1 on page 12 of the Noise Element to
determine suitable locations for land uses based on community noise levels when amending the Gen-eral
Plan land use map and Zoning Map or evaluating new development projects, siting public facili-ties,
and roadway improvement.
The standards in Figure 1 on page 12 of the Noise Element provide land use compatibility standards
based on 24- hour average noise levels, and are the overall standards for acceptability of the noise en-vironment
for noise- sensitive land uses.
Specific additional standards ( for example, for peak or hourly noise levels) based on the unique char-acteristics
of specific noise sources or sensitivities of various land uses may be adopted by the Com-munity
Development Department to supplement these standards as appropriate. However, such stan-dards
shall not be less restrictive than the standards of Figure 1 on page 13.
Projects that would result in exceedance of these standards may require special investigations and
mitigation.
Responsibility. Community Development Department.
Cost and Funding. Low, within normal budget allocation and responsibilities of Department. No
new staff required.
Effectiveness in Reducing Noise Problems. Standards are absolutely required as a foundation
for programs to address existing problems and prevent future ones.
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4.2. Interior Noise and Sound Insulation Standards.
Objective. Prevent noise problems for noise- sensitive land uses by requiring noise barriers or sound
insulation where necessary to achieve acceptable interior noise levels.
Program. This is a continuation of an existing program of enforcement and implementation of the
California interior noise standards. Further, require that new projects be evaluated based on roadway
and other noise impact anticipated at General Plan buildout rather than based on existing noise levels.
The City has extended the applicability of the noise standards to include single- family detached resi-dential
units. Applying this standard to single- family residences has substantial benefits and should
be continued. State noise standards currently apply only to multi- family residential units. Because
single- family residential units are part of the City’s housing stock that must last for a long period of
time through many cycles of ownership, it is appropriate that single- family detached residential units
meet the same noise standards as multi- family units.
Responsibility. Community Development Department.
Cost and Funding. Enforcement of existing standards is a current activity, within normal budget
allocation and responsibilities of Department. No new staff required.
Extension of the standards to new single- family residential development will require action by the City
to adopt the standards for single- family residential units. Also, additional effort in public education,
development of standard conditions, plan review, and site inspection will be required on a continuing
basis, a minor incremental addition to existing costs of building inspection. Training for building in-spectors
may be appropriate to alert them to issues in providing sound insulation for single- family
residential units and extending the geographic area where the City evaluates sound insulation per-formance
of structures.
Because current California energy standards in general require double- pane windows and good weath-erstripping
around openings, no additional sound insulation requirements are expected for single-family
residences except in areas exposed to very high noise levels (“ normally unacceptable” for resi-dential
development).
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4.3. Arterial Street Noise Abatement Program.
Objective. Minimize the noise impact of traffic on arterial streets in noise- sensitive areas.
Program. This program includes a number of components which can work together to minimize the
noise impact of traffic on arterial streets where such roadways pass through noise- sensitive areas
such as near schools and residences.
4.3.1. Rubberized Asphalt Treatment Program.
Program. The Citywide steet pavement resurfacing program currently uses asphalt rubber hot mix as
a maintenance strategy that is also effective in reducing traffic noise.
Effects. Rubberized asphalt has been found to reduce noise levels from arterial roadways by 1 to 3
decibels compared to untreated roadways by minimizing tire noise. The treatment gradually loses its
effectiveness over time, but continues to provide some noise reduction over the life of the treatment,
up to 20 years. Given the limitations on other methods of reducing arterial roadway noise, this meas-ure
has potential to achieve measurable reductions in roadway noise at reasonable cost. This measure
is most effective in areas with relatively high speeds where light duty vehicle tire noise is the most
important component of vehicle noise.
Costs and Other Considerations. Rubberized asphalt treatment loses some of its sound deaden-ing
effect with time, and achieves full effect when the road is newly surfaced. The City has found that
the rubberized asphalt is as good as or better than other surface treatments in terms of roadway life
and maintenance.
The cost of this program is funded through the same sources as other transportation programs. This
program may include funds from the project traffic noise mitigation program if such a program is es-tablished.
Responsibility. Public Works Department.
4.3.2. Arterial Roadway Noise Barrier Wall Program.
Objective. This program is intended to minimize noise impact of arterial streets on adjacent uses
and on ambient noise levels throughout the City by requiring that noise barrier walls be constructed in
new development projects, roadway extension or roadway widening projects where such walls would
be effective in preventing or reducing noise problems.
Program. This program includes construction of noise barrier walls along arterial streets where such
walls can be effective in minimizing existing noise problems and can be implemented without signifi-cant
adverse impacts on site access and aesthetic character of roadways.
In addition, many existing noise barrier walls or decorative project boundary walls are in need of
maintenance or could be made more effective as noise barriers with physical modifications. Improve-ment
of such walls to improve their performance in reducing noise levels in noise- sensitive areas may
also be funded by this program as appropriate. Where walls are located on private property, ease-ments
or agreements may be required with property owners.
Figure 6 on page 45 shows the status of existing arterial roadway barrier walls in the City. Figure 7 on
page 47 shows the noise abatement effectiveness ( in general terms) of existing arterial street noise
barriers.
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Figure 6. Condition of Existing Arterial Roadway Walls
11 x 17 foldout
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Figure 7. Noise Abatement Effectiveness of Arterial Barrier Walls
11 x 17 foldout
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Cost and Funding Sources. In general, noise barrier walls for arterial roadways are expected to be
constructed at the time land is developed and are funded by developers. Walls are to be maintained by
owners or homeowners associations, not by the City.
In some cases, noise barrier wall construction may be funded through noise mitigation fees levied on
new development projects, or may be constructed as project- specific mitigation measures.
4.3.3. Arterial Roadway Sound Insulation and Noise Barrier Mitigation Program.
Objective. Mitigate cumulative impacts of new development on vehicle noise levels throughout the
City through funding of construction or improvement of noise barrier walls and provision of sound
insulation for existing residences and other noise- sensitive land uses.
Program. Under this optional program, new residential, commercial and industrial developments
which result in increases in traffic volume on roadways in the City would be required to pay a noise
mitigation fee to fund noise abatement projects in noise- sensitive areas of the City which are most
affected by cumulative increases in traffic noise. Under this program, the City would establish priori-ties
for areas in which noise abatement projects can have the greatest benefit, develop programs in-cluding
barrier wall construction and sound insulation, and fund noise abatement programs as fund-ing
is available from development projects.
Because most areas of the City are near their development capacity, and substantial noise impacts re-sulting
from growth are not expected except in unusual cases, the application of this program may be
limited.
Responsibility. Community Development and Public Works Departments.
Cost and Funding Sources . This program if implemented would require the development of a pro-gram
including specific projects, a cost estimate, a justification for assignment to development pro-jects
( to establish a “ nexus” between costs and fees), and preparation and adoption of the program by
the City Council by resolution or ordinance. Cost of establishing the program could range between
$ 25,000 and $ 50,000 or more, and should be weighed against the potential benefits achieved and the
potential for revenue from development projects. Ongoing management of the program would require
staff review of individual projects and calculation of project fees.
Costs of construction of arterial roadway walls may range from $ 50.00 to $ 800.00 per linear foot or
more, depending on the height of the wall, materials used in construction, structural requirements,
aesthetics, graffiti protection, landscaping and irrigation systems required, etc. Costs would be ex-pected
to increase annually with typical construction costs.
4.3.4. Noisy Vehicle Code Enforcement Program.
Objective. Minimize nuisance noise from particularly noisy vehicles.
Program. This program includes the active enforcement of vehicle code provisions limiting engine
noise from motor vehicles, limiting muffler modifications on motor vehicles, and limiting noise from
sound systems in motor vehicles.
Responsibility. Police Department, City Attorney
Cost and funding sources . Additional cost of this program will include funding of training and
equipment of Police Department staff involved in the enforcement program. While such programs are
normally enforced on a complaint basis, periodic active enforcement of such laws can substantially
reduce the number of violations since most violations are a result of a few non- complying vehicles
and individuals. Equipment purchase and regular calibration ( potentially shared with noise ordinance
enforcement costs with the Community Development Department), staff training, and one or two fo-cused
periods involving a team of two officers for part of one shift for a week would be expected to
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cost approximately $ 5,000 to $ 10,000 per year. Cases which are taken to court for enforcement may
involve additional costs. Funding would be from the City’s general fund.
4.3.5. Arterial Roadway Speed Control
Objective: Minimize roadway noise by reducing vehicle speed.
Program: This program involves establishment and enforcement of lower speed limits on selected ar-terial
roadways through noise- sensitive areas where speed can be effective in minimizing the amount
of noise- sensitive land use exposed to “ normally unacceptable” noise levels by City standards. If re-ducing
speed limits is not feasible or enforcible, consider focusing public relations efforts such as a
special “ quiet streets” program with signage and public outreach, and seek special legislation to per-mit
use of speed limits for noise abatement in special situations.
Figure 5 on page 31 illustrates the potential effect of reductions in speed limit and enforcement of
speed laws for noise abatement.
Responsibility: Community Development Department, Public Works Department, Police Department
Cost and Funding: Some additional costs will be involved in order to identify suitable areas for ap-plication
of this strategy, perform necessary studies to justify establishment of lower speed limits,
install special signage, and enforce speed limits. If only two or three short stretches of roadway are
involved, cost could be in the range of $ 10,000- 20,000 to establish these areas, with some annual
enforcement costs. A citywide program of extensive speed limit changes could be substantially more
expensive.
Effectiveness in Reducing Noise Problems: A reduction in speed from 45 mph to 35 mph on an arterial
roadway can be as effective as a 40% reduction in traffic volume or rubberized asphalt treatment.
While the noise benefits are limited, this is one of a very few methods of reducing noise conflicts from
existing traffic, and is worth investigation in noise impact areas.
State law limits the ability of local agencies to enforce speed limits lower than determined appropriate
by speed surveys unless specific safety conditions dictate lower speed limits. Special legislation
would be required to add noise to the considerations that can be used in setting speed limits. How-ever,
some benefit may be possible from a “ slow and quiet” public relations program with special
signage and other measures focused on specific problem roadways.
4.4. Noise Review of Project Time Extensions.
Objective. Ensure that previously approved projects which have not yet been constructed and re-quest
time extensions provide noise analysis and mitigation measures based on current conditions.
Program. This program involves the review for noise impact and noise sensitivity of projects that
have remained undeveloped following approval for a considerable period of time ( such as 5 years or
more). In considering requests for time extensions for such projects, the City may require additional
noise mitigation measures or noise studies, based on changes in the project, changes in land uses
adjacent to the project, or changes in the noise environment of the project or surrounding areas.
Responsibility. Community Development.
Costs and Funding. Moderate additional costs for project reviews, should be funded by fees for
project extensions and payment of noise study costs by project applicants.
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4.5. Freeway Noise Barrier Wall Completion Program.
Objective. Ensure that aesthetically acceptable freeway noise barrier walls are ultimately constructed
in all locations where such walls would be effective in minimizing noise problems. Priority should be
given to locations where the benefits of constructing the walls are greatest, including the areas ex-posed
to highest noise levels, and the areas where the walls are most effective in reducing noise im-pact
for the largest number of people.
Program. This program has three primary components. The first involves coordination with the Ven-tura
County Transportation Commission ( VCTC) and Caltrans for prioritizing, funding, design, sched-uling
and construction of noise barrier walls. The second involves advocacy to increase state or other
funding for Caltrans noise barriers. The third involves City participation to the extent feasible in con-structing
barriers in locations where barriers are effective but may not meet Caltrans criteria for barrier
wall construction. This participation may be funded from project noise impact mitigation fees or
other funds as available.
4.5.1. Caltrans Noise Barrier Construction Advocacy and Monitoring.
Objective: Ensure that noise barriers are constructed along freeways wherever they can be effective
in protecting noise- sensitive land uses from freeway noise impacts.
Program. This program involves continuing coordination with the Ventura County Transportation
Commission and Caltrans for prioritizing, funding, design, scheduling and construction of noise bar-rier
walls.
Responsibility. City Manager, Community Development Department, Public Works Department.
Costs and Other Considerations Recent legislation ( SB 45) has transferred much of the responsi-bility
to the Ventura County Transportation Commission for identifying, prioritizing and funding free-way
sound walls countywide. Since the legislation is new, implementation details are still being de-veloped.
Funding for freeway noise barriers is anticipated to be from the State Transportation Im-provement
Program and would require that Caltrans design and construct the sound walls. Caltrans
currently has an extensive backlog of sound wall work and delays are possible. Sound walls con-structed
by Caltrans are generally more expensive than those constructed by local agencies.
In the City of Thousand Oaks, the Route 23 Freeway is scheduled to be widened. New sound walls will
be included in the widening project, which is scheduled for the year 2004. Other sound walls identi-fied
along the Route 101 Freeway or the Route 23 Freeway not associated with the widening will be a
part of the priority process noted in the Program section above. The City should monitor the sound
wall process and develop an advocacy program, if needed, for priority and funding of local noise barri-ers.
To the extent that the advocacy program will require special studies to justify expenditures, travel to
Sacramento, special efforts by legislative advocates, or other actions, the program may require hiring
of others and expenditures for City staff efforts outside of the normal budgets for Community Devel-opment
and Public Works. The normal budgets of the Community Development and Public Works De-partments
provide for regular consultation with other agencies such as Caltrans on current projects as
a normal departmental function, but do not provide for special studies or unusual efforts by City staff,
consultants or legislative advocates. An additional effort could require additional funding of $ 10,000
to $ 50,000 per year depending on actions contemplated.
If the program requires an additional full- time staff member for the Public Works Department, costs
could exceed $ 100,000 per year for the construction period, plus the cost of additional consultants
for special studies.
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4.5.2. Legislative Advocacy of Caltrans Noise Barrier Funding Increases.
Program. This program involves legislative advocacy to increase the funding for installation of noise
barriers on freeways, so that the installation of these barriers can be accelerated.
Responsibility. City Council, City Manager, Community Development Department, Public Works De-partment
Costs and Other Considerations. The Caltrans schedule for implementing noise barrier walls
along freeways is funded at a level that leaves a substantial backlog in construction of such walls
throughout the state. The City should be able to gain cooperation of some other cities and counties
to promote a faster implementation of the barrier wall program. However, legislative advocacy is an
expensive and unpredictable means of reaching objectives. Cost may range from negligible for a low-effort
program including a few contacts by City lobbyists or the League of California Cities, to sub-stantial
costs ($ 20,000 or more startup costs, plus annual advocacy until adopted) for a higher level of
effort including drafting legislation and gaining support of other jurisdictions.
4.5.3. Freeway Noise Barrier Construction
Objective: Provide funding or coordinate funding from other sources to the extent necessary to com-plete
noise barriers that are needed but cannot be funded by Caltrans.
Program. Identify locations where noise barriers are needed but cannot or will not be funded by Cal-trans,
identify other funding sources, and fund or assist in funding construction of these barriers to
the extent revenues can be found for this purpose. Examples of the types of programs that might be
considered are Community Development Block Grant funds, capital improvements funds from noise
abatement development fees, local assessment districts paid for by those who benefit from the barrier
wall, or other programs as available.
Responsibility: City Manager, Community Development Department, Public Works Department
Costs and Other Considerations. According to City staff estimates, noise barrier walls may cost
from $ 200 to as much as $ 800 per linear foot. For lots with a 100- foot freeway frontage, the cost of
the wall per residence would be approximately $ 20,000 to $ 80,000. Greatest benefits occur to those
immediately adjacent to the noise barrier, so the number of people benefited substantially by a typical
sound wall is small. Although the barrier may reduce freeway noise by 10 decibels or more for those
nearest the wall, the benefits to residences which are separated from the freeway by other residences
is likely to be 3 dB or less because of the protection provided by the first row of residences. Thus the
benefit area is small in most cases, making expenditure of City funds for the entire cost of the pro-gram
difficult to justify, and making walls difficult to fund through an assessment district. For the
example of a 100- foot frontage, the cost per year of an assessment district to construct a barrier wall
paid for by those adjacent to the wall would be approximately $ 2,000 per year for 10 to 20 years.
Community Development Block Grant funds may be available to fund barrier walls if a substantial
benefit to low- and moderate- income persons can be found in each particular case.
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Figure 8. Existing and Proposed Freeway Noise Barriers
.
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Figure 8: Back page
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4.6. Noise Considerations in Environmental Impact Reports and
Negative Declarations.
Objective. The purpose of this program is to identify and avoid potential noise problems at the pro-ject
level when environmental impact of projects is considered in accordance with the California Envi-ronmental
Quality Act ( CEQA).
4.6.1. Thresholds of Significant Project and Cumulative Noise Impact
Under the California Environmental Quality Act, an Agency must determine whether or not a project
has potentially significant adverse environmental effects in a variety of categories of effects. The fol-lowing
thresholds of potentially significant effects are adopted as the thresholds of significance to be
used in Environmental Impact Reports and Negative Declarations prepared for projects for which the
City or Redevelopment Agency is the Lead Agency under CEQA.
Table 9. Thresholds of Significance for Noise Impact
If the annual average noise
level with the proposed pro-ject,
cumulative projects and
General Plan buildout in an
area currently used for or
designated in the General
Plan for a noise- sensitive
land use1 is expected to be:
A significant project or cu-mulative
impact may result
if the change in annual av-erage
noise levels from ex-isting
conditions due to all
sources in an area currently
used for or designated in
the General Plan for a
noise- sensitive land use1 is:
The project alone may
be considered to make
a substantial contribu-tion
to significant cu-mulative
impact if the
change in annual aver-age
noise level due to
the project is:
Less than 55 dB CNEL Not significant for any change in
noise level
Not significant for any change
in noise level
55- 60 dB CNEL Equal to or greater than 3.0 decibels Equal to or greater than 1.0
decibels
60- 70 dB CNEL Equal to or greater than 1.5 decibels Equal to or greater than 0.5
decibels
Greater than 70 dB CNEL Equal to or greater than 1.0 decibels Equal to or greater than 0.5
decibels
1. A noise- sensitive land use is a use for which the lower limit of the noise level considered “ normally unaccept-able”
for development because of noise impact is 70 dB CNEL or lower. In identifying land use areas, areas
which are undevelopable for noise- sensitive uses because of slope, devopment restriction, easement, etc., or
which are used for non- noise- sensitive components of a multiple- use or mixed- use project, should not be con-sidered
noise- sensitive.
Exceptions.
1. Development of single- family or multi- family residential uses in an infill project in an existing
residential area which is designated for development for residential uses in the General Plan, and for
which a sound insulation study has been prepared by a qualified acoustical engineer or other sound
insulation specialist, and for which sound insulation is included in the proposed project to meet state
standards for interior noise levels for multi- family residential development, shall not be considered to
have a significant adverse effect when considering the exposure of the project itself to noise levels
exceeding the standards of this Noise Element. ( Off- site impacts of such projects should still be
considered in determini