GUIDELINES FOR THE PREPARATION AND CONTENT OF THE NOISE ELEMENT OF THE GENERAL PLAN
OUTLINE
I. INTRODUCTION
The Noise Element of the General Plan provides a basis for comprehensive local programs to control and abate environmental noise and to protect citizens from excessive exposure. The fundamental goals of the Noise Element are:
To provide sufcient information concerning the community noise environment so thatnoise may be effectively considered in the land use planning process. In so doing, thenecessary groundwork will have been developed so that a community noise ordinance ma ybe utilized to resolve noise complaints.
To develop strategies for abating excessive noise exposure through costeffective mitigating measures in combination with zoning, as appropriate, to avoid incompatible land uses.
To protect those existing regions of the planning area whose noise environments are deemed acceptable and also those locations throughout the community deemed "noise sensitive."
To utilize the denition of the community noise environment, in the form of CNEL orLdn noise contours as provided in the Noise Element for local compliance with the State Noise Insulation Standards. These standards require specied levels of outdoor to i ndoor noise reduction for new multifamily residential constructions in areas where the outdoor noise exposure exceeds CNEL (or Ldn) 60 dB.
The 1976 edition of the Noise Element Guidelines, prepared by the State Departmentof Health Services (DOHS), was a result of SB 860 (Beilenson, 1975), which became effective January 1, 1976. SB 860, among other things, revised and claried the requireme nts for the noise element of each city and county general plan and gave the DOHS authority to issue guidelines for compliance thereto. Compliance with the 1976 version of these guidelines was mandated only for those noise elements which were not submitted to the Ofce of Planning and Research by the effective date of SB 860 and to subsequent revisions of previously submitted noise elements.
A comparison between the 1976 Noise Element Guidelines and this revised edition will not reveal substantial changes. The basic methodology advanced by that previous edition remains topical. Where necessary, code references have been updated and the text revised to reect statutory changes.
II. DEFINITIONS
Decibel, dB: A unit of measurement describing the amplitude of sound, equal to 20 times the logarithm to the base 10 of the ratio of the pressure of the sound measured to the reference pressure, which is 20 micropascals (20 micronewtons per square meter).
A-Weighted Level: The sound level in decibels as measured on a sound level meter using the Aweighting lter network. The A-weighting lter deemphasizes the very low and very high frequency components of the sound in a manner similar to the response of th e human ear and gives good correlation with subjective reactions to noise.
L10: The Aweighted sound level exceeded ten percent of the sample time. Similarly, L50, L90 etc.
Leq: Equivalent energy level. The sound level corresponding to a steady state soundlevel containing the same total energy as a time varying signal over a given sample period. Leq is typically computed over 1, 8, and 24hour sample periods.
CNEL: Community Noise Equivalent Level. The average equivalent A-weighted sound levelduring a 24hour day, obtained after addition of ve decibels to sound levels in the evening from 7 p.m. to 10 p.m. and after addition of 10 decibels to sound levels in the night from 10 p.m. to 7 a.m.
Ldn: DayNight Average Level. The average equivalent Aweighted sound level during a 24hour day, obtained after addition of 10 decibels to sound levels in the night after 10 p.m. and before 7 a.m.
Note: CNEL and Ldn represent daily levels of noise exposure averaged on an annual or daily basis, while Leq represents the equivalent energy noise exposure for a shorter time period, typically one hour.
Noise Contours: Lines drawn about a noise source indicating equal levels of noise exposure. CNEL and Ldn are the metrics utilized herein to describe annoyance due to noise and to establish land use planning criteria for noise.
Ambient Noise: The composite of noise from all sources near and far. In this context, the ambient noise level constitutes the normal or existing level of environmental noise at a given location.
Intrusive Noise: That noise which intrudes over and above the existing ambient noise at a given location. The relative intrusiveness of a sound depends upon its amplitude, duration, frequency, and time of occurrence, and tonal or informational content as well as the prevailing noise level.
Noisiness Zones: Dened areas within a community wherein the ambient noise levels are generally similar (within a range of 5 dB, for example). Typically, all other things being equal, sites within any given noise zone will be of comparable proximity to major noise sources. Noise contours dene different noisiness zones.
III. NOISE ELEMENT REQUIREMENTS
California Government Code Section 65302(f):
A noise element shall identify and appraise noise problems in the community. The noise element shall recognize the guidelines established by the Ofce of Noise Control in the State Department of Health Services and shall analyze and quantify, to the extent practicable, as determined by the legislative 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 online railroad operations and ground rapid transit systems.
(4) Commercial, general aviation, heliport, helistop, and military airport operations, aircraft
overights, 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 classication yards.
(6) Other ground stationary sources identied by local agencies as contributing to the
community noise environment.
NATURE OF THE GENERAL PLAN
Noise contours shall be shown for all of these sources and stated in terms of community noise equivalent level (CNEL) or daynight average level (Ldn). The noise contours shall be prepared on the basis of noise monitoring or following generally accepted noise modeling techniques for the various sources identied in paragraphs (1) to (6), inclusive.
The noise contours shall be used as a guide for establishing a pattern of land uses in the land use element that minimizes the exposure of community residents to excessive noise.
The noise element shall include implementation measures and possible solutions that address existing and foreseeable noise problems, if any. The adopted noise element shall serve as a guideline for compliance with the state's noise insulation standards.
IV. PROCESS OF NOISE ELEMENT DEVELOPMENT
The sequential steps for development of a noise element as an integral part of a community's total noise control program are illustrated in the ow diagram of gures 1A and 1B. The concept presented herein utilizes the noise element as the central focus of the community's program and provides the groundwork for all subsequent enforcement efforts. The process may be described in terms of four phases:
A. Noise Environment Denition
B. Noise Compatible Land Use Planning
C. Noise Mitigation Measures
D. Enforcement
These phases encompass a total of eighteen dened tasks, the rst thirteen of which relate directly to the statutory requirements contained in section 65302(f), while the remainder relate to critical supportive programs (noise ordinances etc.). Citations from section 65302(f)are contained within quotation marks.
Figure 1A
Figure 1B
A. Noise Environment Denition
The purpose of this phase is to adequately identify and appraise the existing and future noise environment of the community in terms of Community Noise Equivalent Level (CNEL) or DayNight Average Level (Ldn) noise contours for each major noise source a nd to divide the city or county into noise zones for subsequent noise ordinance application.
Step 1
Identify a specic individual or lead agency within the local government to be responsible for coordination of local noise control activities. This individual or agency should be responsible for coordinating all intergovernmental activities and subsequent enforcement efforts.
Step 2
Review noise complaint les as compiled by all local agencies (police, animal control, health, airport, trafc department, etc.) in order to assess the following:
(1) Location and types of major offending noise sources.
(2) Identication of noise sensitive areas and land uses.
(3) Community attitudes towards specic sources of noise pollution.
(4) Degree of severity of noise problems in the community.
(5) Relative signicance of noise as a pollutant.
Step 3
Specically identify major sources of community noise based upon the review of complaint les and interagency discussion and the following statutory subjects:
(1) Highways and freeways.
(2) Primary arterials and major local streets.
(3) Passenger and freight online railroad operations and ground rapid transit systems.
(4) Commercial, general aviation, heliport, helistop, and military airport operations, aircraft overights, jet engine test stands, and all other ground facilities and mainte nance functions related to airport operation.
(5) Local industrial plants, including, but not limited to, railroad classication yards.
(6) Other ground stationary noise sources identied by local agencies as contributing to the community noise environment.
In addition, the land uses and areas within the community that are noise sensitive should be identied at this time.
Step 4
Given the identication of major noise sources and an indication of the community's attitude toward noise pollution (when available), it is advisable to conduct a community noise survey. The purposes of the survey are threefold:
First and foremost, to dene by measurement the current noise levels at those sites deemed noise sources and to establish noise level contours around them. The noise contours must be expressed in terms of CNEL or Ldn.
Second, the collected data will form the basis for an analysis of noise exposure from major sources.
Finally, the survey should dene the existing ambient noise level throughout the community. Intrusive noises, over and above this general predetermined ambient level, may then be controlled through implementation of a noise ordinance.
Step 5
Given the denition of existing ambient noise levels throughout the community, one may proceed with a classication of the community into broad regions of generally consistent land use and similar noise environments. Because these regions will be varying distances from identied major noise sources, the relative levels of environmental noise will be different from one another. Therefore, subsequent enforcement efforts and mitigating measures may be oriented towards maintaining quiet areas and improving noisy ones.
Step 6
Directing attention once again to the major noise sources previously identied, it is essential to gather operations and activity data in order to proceed with the analytical noise exposure prediction. This data is somewhat source specic, but generally should consist of the following information and be supplied by the owner/operator of the source:
(1) Average daily level of activity (trafc volume, ights per day, hours of operation, etc.).
(2) Distribution of activity over day and night time periods, days of the week, and seasonal variations.
(3) Average noise level emitted by the source at various levels of activity.
(4) Precise source location and proximity to noise impacted land uses.
(5) Composition of noise sources (percentage of trucks on highway, aircraft eet mix, industrial machinery type, etc.).
Step 7
In addition to collecting data on the variables affecting noise source emission for the existing case, future values for these parameters need to be assessed. This is best accomplished by correlating the noise element with other general plan elements (i.e. land use, circulation, housing, etc.) and regional transportation plans and by coordination with other responsible agencies (Airport Land Use Commission, Caltrans etc.).
Step 8
Analytical noise exposure modeling techniques may be utilized to develop sourcespecic noise contours around major noise sources in the community. Noise contours must be prepared on the basis of noise monitoring or following generally accepted noise modeling techniques.
Simplied noise prediction methodologies are available through the State Department of Health Services for highway and freeway noise, railroad noise, simple xed stationary and industrial sites, and general aviation aircraft (with less than twenty percent commercial jet aircraft activity two engine jet only). Noise contours for larger airport facilities and major industrial sites are sufciently complex that they must be developed via sophisticated computer techniques available through recognized acoustical consulting rms. (Airport contours, generally, have already been developed in accordance with requirements promul gated by the Division of Aeronautics: Noise Standards Sections 5000 et seq. of Title 21, California Code of Regulations.)
Although considerable effort may go into developing noise contours which, in some instances, utilize rather sophisticated digital programming techniques, the present stateoftheart is such that their accuracy is usually no better than +/ 3 dB. In fact, the accuracy of the noise exposure prediction decreases with increasing distance from the noise source. In the near vicinity of the source, prediction accuracy may be within the range of +/ 1 dB, while at greater distances this may deteriorate to +/ 5 dB or greater. At greater distances, meteorological and topographic effects, typically not totally accounted for in most models, may have signicant inuence. Thus, while dealing with the concept of noise contours, it is best not to think of them as absolute lines of demarcation on a map (such as topographical contours), but rather as bands of similar noise exposure.
In addition to assessment of the present day noise environment, it is recommended that the noise exposure data be projected through the time horizon of the general plan. The noise
element should be updated and corrected every ve years and, at that time, the forecasted noise exposure be projected an additional ve years.
B. Noise Compatible Land Use Planning
A noise planning policy needs to be rather exible and dynamic to reect not only technological advances in noise control but also economic constraints governing application of noise control technology and anticipated regional growth and demands of the community. In the nal analysis, each community must decide the level of noise exposure its residents are willing to tolerate within a limited range of values below the known levels of health impairment.
Step 9
Given the denition of the existing and forecasted noise environment provided by the Phase A efforts, the locality preparing the noise element must now approach the problem of dening how much noise is too much. Guidelines for noise compatible land use are presented in gure 2. The adjustment factors given in Table 1 may be used in order to arrive at noise acceptability standards which reect the noise control goals of the community, the particular community's sensitivity to noise (as determined in Step 2), and their assessment of the relative importance of noise pollution.
Step 10
As a prerequisite to establishing an effective noise control program, it is essential to know, in quantitative terms, the extent of noise problems in the community. This is best accomplished by determining, for each major noise source around which noise contours have been developed, the number of community residents exposed and to what extent. It is also useful to identify those noise sensitive land uses whose noise exposure exceeds the recom mended standards given in gure 2. The exposure inventory can be accomplished by using recent census data, adjusted for regional growth, and tabulating the population census blocks within given noise contours.
Step 11
Once the noise exposure inventory is completed, the relative signicance of specic noise sources in the community (in terms of population affected) will become apparent. The local agencies involved may wish to use this information to orient their noise control and abatement efforts to achieve the most good. Clearly, control of certain major offending sources will be beyond the jurisdiction of local agencies; however, recognition of these limitations should prompt more effective land use planning strategies.
Step 12
A major objective of the noise element is to utilize this information to ensure noise compatible land use planning: The noise contours must be used as a guide for establishing a pattern of land uses in the land use element to minimize community residents' exposure to excessive noise.
The intent of such planning is to:
(1) Maintain those areas deemed acceptable in terms of noise exposure.
(2) Use zoning or other land use controls in areas with excessive noise exposure to limit uses to those which are noise compatible and to restrict other less compatible uses.
C. Noise Mitigation Measures
Step 13
Based upon the relative importance of noise sources in order of community impact and local attitudes towards these sources, the noise element must include implementation measures and possible solutions that address existing and foreseeable noise problems, if any. Selection of these noise mitigation measures should be coordinated through all local agencies in order to be most effective.
Minimization of noise emissions from all local government-controlled or sanctioned activities should by a priority item. This includes low noise specications for new or county -owned and operated vehicles (and noise reduction retrotting where economically possible) and noise emission limits on public works projects.
Cities and counties should insure that public buildings (especially schools) are sufciently insulated to allow their intended function to be uninterrupted by exterior noise. Local agencies can work with state and federal bodies to minimize transportation noise, primarily through transit way design, location, or conguration modications.
Additional measures might include such policies as limitation of siren useage by police, re, and ambulance units within populated areas. Animal control units may be encouraged to minimize barking dog complaints through use of an improved public relations campaign termed "Animal Philosophy." This involves working with pet owners to determine why the dog barks and attempting solutions rather than just issuing citations. Local zoning and subdivision ordinances may require the use of noise reducing building materials or the installation of sound insulating walls along major roads in new construction and subdivi sions.
In general, local noise reduction programs need to address the problems specic to each community, with the ultimate goals being the reduction of complaint frequency and the provision of a healthful noise environment for all residents of the community.
The following steps are beyond the scope of the noise element requirements, but pertain to coordination with other state noise control programs and achievement of the goals set forth in the noise element through development of an active local noise control effort.
Step 14
While the noise element identies problem areas and seeks to develop medium and longrange solutions to them, a community noise ordinance is the only viable instrument for shortterm or immediate solutions to intrusive noise. A model noise ordinance which may be tailored to the specic needs of a given community by simply incorporating those sections deemed most applicable has been developed by the Department of Health Services. The model ordinance also suggests a cure for non-stationary or transient types of noise events, for which noise contours are generally meaningless.
D. Enforcement
To adequately carry out the programs identied in the noise element and to comply with State requirements for certain other noise control programs, specic enforcement programs are recommended at the local level.
Table 1
Corrections to be Added to the Measured Community Noise
Equivalent Level (CNEL) to Obtain Normalized CNEL
Step 15
Adopt and apply a community noise ordinance for resolution of noise complaints.
Step 16
Recent studies have shown that the most objectionable feature of trafc noise is the sound produced by vehicles equipped with illegal or faulty exhaust systems. In addition, such hot rod vehicles are often operated in a manner that causes tire squeal and excessively loud exhaust noise. There are a number of statewide vehicle noise regulations that can be enforced by local authorities as well as the California Highway Patrol. Specically, Sections 23130, 23130.5, 27150, 27151, and 38275 of the California Vehicle Code, as well as excessive speed laws may be applied to curtail this problem. Both the Highway Patrol and the State Department of Health Services (through local health departments) are available to aid local authorities in code enforcement and training pursuant to proper vehicle sound level measurements.
Step 17
Commercial and public airports operating under a permit from the Caltrans Division of Aeronautics are required to comply with both the State Aeronautics standards governing aircraft noise and also all applicable legislation governing the formation and activities of a local Airport Land Use Commission (ALUC). The function of the ALUC is, among other things, to develop a plan for noise compatible land use in the immediate proximity of the airport. The local general plan must be reviewed for compatibility with this Airport Land Use Plan and amended if necessary (Public Utilities Code Section 21676). Therefore, the developers of the noise element will need to coordinate their activities with the local ALUC to ensure that compatible standards are utilized throughout the community and that the noise element develops as part of a coherent master plan, of which the ALUP forms an integral component.
Step 18
The adopted noise element must serve as a guideline for compliance with the State's noise insulation standards.Recognizing the need to provide acceptable habitation environments, State law requires noise insulation of new multifamily dwellings constructed within the 60 dB (CNEL or Ldn) noise exposure contours. It is a function of the noise element to provide noise contour information around all major sources in support of the sound transmission control standards (Appendix, Chapter 2-35, Part 2, Title 24, California Code of Regula tions).
V. RELATIONSHIP OF THE NOISE ELEMENT TO OTHER GENERAL PLAN ELEMENTS
The noise element is related to the land use, housing, circulation, and open space elements. Recognition of the interrelationship of noise and these four mandated elements is necessary in order to prepare an integrated general plan. The relationship between noise and these four elements is briey discussed below.
Land Use A key objective of the noise element is to provide noise exposure information for use in the land use element. When integrated with the noise element, the land use element will show acceptable land uses in relation to existing and projected noise contours. Section
65302(f) of the Government Code states that:
The noise contours shall be used as a guide for establishing a pattern of land uses in the land use element that minimizes the exposure of community residents to excessive noise.
Housing The housing element considers the provision of adequate sites for new housing and standards for housing stock. Since residential land use is among the most noise sensitive, the noise exposure information provided in the noise element must be considered when planning the location of new housing. Also, state law requires special noise insulation of new multifamily dwellings constructed within the 60 dB (CNEL or Ldn) noise exposure contour. This requirement may inuence the location and cost of this housing type. In some cases, the noise environment may be a constraint on housing opportunities.
Circulation The circulation system must be correlated with the land use element and is one of the major sources of noise. Noise exposure will thus be a decisive factor in the location and design of new transportation facilities and the possible mitigation of noise from existing facilities in relation to existing and planned land use. The local planning agency may wish to review the circulation and land use elements simultaneously to assess their compatibility with the noise element.
Open Space Excessive noise can adversely affect the enjoyment of recreational pursuits in designated open space. Thus, noise exposure levels should be considered when planning for this kind of openspace use. Conversely, open space can be used to buffer sensitive land uses from noise sources through the use of setback and landscaping. Open-space designation can also effectively exclude other land uses from excessively noisy areas.
VI. SELECTION OF THE NOISE METRIC
The community noise metrics to be used in Noise Elements are either CNEL or Ldn (as specied in Section 65302(f)). A signicant factor in the selection of these scales was compatibility with existing quantications of noise exposure currently in use in California. CNEL is the noise metric currently specied in the State Aeronautics Code for evaluation of noise impact at specic airports which have been declared to have a noise problem. Local compliance with the state airport noise standards necessitates that community noise be specied in CNEL. The Ldn represents a logical simplication of CNEL. It divides the day into two weighted time periods (Day 7a.m. to 10 p.m. and Night 10 p.m. to 7a.m.) rather than the three used in the CNEL measure (Day 7a.m. to 7p.m., Evening 7p.m.to 10 p.m., and Night 10 p.m. to 7a.m.) with no signicant loss in accuracy.
VII. CRITERIA FOR NOISE COMPATIBLE LAND USE
Figure 2 (next page) summarizes the suggested use of the CNEL/Ldn metrics for evaluating land use noise compatibility. Such criteria require a rather broad interpretation, as illustrated by the ranges of acceptability for a given land use within a dened range of noise exposures.
Denotation of a land use as "clearly acceptable" on Table 2 implies that the highest noise level in that band is the maximum desirable for existing or conventional construction which does not incorporate any special acoustic treatment. In general, evaluation of land use which falls
Figure 2
LAND USE COMPATABILITY FOR COMMUNITY NOISE ENVIRONMENTS
into the "normally acceptable" or "normally unacceptable" noise environments should include consideration of the type of noise source, the sensitivity of the noise receptor, the noise reduction likely to be provided by structures, and the degree to which the noise source may interfere with speech, sleep, or other activities characteristic of the land use.
Figure 2 also provides an interpretation as to the suitability of various types of construction with respect to the range of outdoor noise exposure.
The objective of the noise compatibility guidelines in Figure 2 is to provide the community
with a means of judging the noise environment which it deems to be generally acceptable. Many efforts have been made to account for the variability in perceptions of environmental noise which exist between communities and within a given community.
Beyond the basic CNEL or Ldn quantication of noise exposure, one can apply correction factors to the measured or calculated values of these metrics in order to account for some of the factors which may cause the noise to be more or less acceptable than the mean response. Signicant among these factors are seasonal variations in noise source levels, existing outdoor ambient levels (i.e., relative intrusiveness of the source), general societal attitudes towards the noise source, prior history of the source, and tonal characteristics of the source. When it is
Figure 3
RANGE OF TYPICAL OUTDOOR NOISE ENVIRONMENTS
EXPRESSED IN TERMS OF DAY-NIGHT SOUND LEVEL (Ldn ), dB
possible to evaluate some or all of these factors, the measured or computed noise exposure values may be adjusted by means of the correction factors listed in Table 1 in order to more accurately assess local sentiments towards acceptable noise exposure.
In developing these acceptability recommendations, efforts were made to maintain consis tency with the goals dened in the Federal EPA document entitled Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety, and the State Sound Transmission Control Standards for multifamily housing. In both of these documents, an interior noise exposure of 45 dB CNEL (or Ldn) is recommended to permit normal residential activity. If one considers the typical range of noise reduction provided by residential dwellings (12 to 18 dB with windows partially open), the 60 dB outdoor value identied as "clearly acceptable" for residential land use would provide the recommended interior environment.
Figure 3 has been included in order to better explain the qualitative nature of community noise environments expressed in terms of Ldn. It is apparent that noise environments cover a broad range and that, in general, if may be observed that the quality of the environment improves as one moves further away from major transportation noise sources.
VIII. BIBLIOGRAPHY
Airport Land Use Planning Handbook. A reference guide for local agencies. Prepared for the California Department of Transportation, Division of Aeronautics by the Metropolitan Transportation Commission and the Association of Bay Area Governments, Oakland, CA July, 1983.
California Code of Regulations. State Building Code, Part 2, Title 24, Appendix Chapter 35; Noise Insulation Standards for Multifamily Housing.
Lynch, Kevin and Hack, Gary: Site Planning. Massachusetts Institute of Technology, Cambridge, MA, 1984.
Peterson, Arnold P.G. and Gross, Ervin E. Jr.: Handbook of Noise Measurement . General Radio Co., Concord, MA, 1974.
Simplied Procedures for Estimating the Noise Impact Boundary for Small and Medium Size Airports in the State of California. Wyle Research Report No. WCR 723, prepared for the California Department of Aeronautics by Wyle Laboratories, May 1973.
Swing, J.W. and Pies, D.B.: Assessment of Noise Environments Around Railroad Operations . Wyle Research Report No. WCR 73-5, Wyle Laboratories, El Segundo, CA, July 1973.
Swing, J.W.: "Estimation of Community Noise Exposure in Terms of Day-Night Average Level Noise Contours." California Ofce of Noise Control, Department of Health, Berkeley, CA, May 1975.
U.S. Department of Housing and Urban Development: Aircraft Noise Impact Planning Guidelines for Local Agencies . Prepared by Wilsey and Ham, (GPO Stock No. 2300-00214), Pasadena, CA, November 1972.
U.S. Department of Transportation, Federal Highway Administration, National Highway Institute: Fundamentals and Abatement of Highway Trafc Noise . (Report No. FHWA-
HHI-HEV-73-7976-1), June 1973.
U.S. Environmental Protection Agency: Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety . (550/9-74-004), March 1974.
Veneklasen, Paul S.: "Development of a Model Noise Ordinance." Performed under contract to the California Ofce of Noise Control, Department of Health, Berkeley, CA, March 1975.
APPENDIX A-1
CALIFORNIA NOISE INSULATION STANDARDS