A city (or county) is not an accident but the result of coherent visions and aims

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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: Defined 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 define different noisiness zones. 
Local airports are subject to the noise requirements of the Federal Aviation Administration and noise standards under the 
California Code of Regulations, 
Title 21, section 5000, et seq
. These standards are designed to encourage the airport proprietor, 
aircraft operators, local governments, pilots, and Caltrans to work cooperatively to diminish excessive aircraft noise impacts. 
However, the U.S. Secretary of Transportation must review and approve all local airport noise and access restrictions adopted 
after 1990, and they must meet specified criteria (
49 U.S.C. § 47524)
. 
Proposed school sites within two nautical miles of an airport runway or potential runway in an airport master plan are subject to 
review by CalTrans Division of Aeronautics (
Cal. Code Regs., tit. 21, § 3570
, and
 Ed. Code § 17215
). The regulations authorize 
CalTrans to object to the acquisition or lease of a school site within a 65 decibel annual CNEL aircraft noise contour. If Caltrans 
recommends against it based on noise considerations, the board may not acquire or lease the site (
Ed. Code § 17215(d)
).
Specific considerations for noise generated by or related to military facilities can be found in the 
California Advisory Handbook 
for Community and Military Compatibility Planning
.
Noise Measurement and Modeling
The local planning agency should select the method of measurement or modeling that best suits its needs, either CNEL or Ldn. 
See 
Appendix D
 for more information about these two types of noise measurements and noise descriptors. 
Noise should be measured at multiple receptors. The volume of traffic noise, construction noise, and the noise of an 
environment (such as loud schools, playgrounds, or agricultural areas) depends on many factors, including the location of 
dwellings and the location and types of trips made in neighborhoods en route to school, work, or shopping.
iv
 Measuring noise 
at multiple receptors throughout a community will ensure that the noise element is accurate. The noise element should address 
the following: 
• Major noise sources, both mobile and stationary
• Ground borne noise, ground borne vibration from public transit, freight trains, or light rail transit lines

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• Existing and projected levels of noise and noise contours for major noise sources
• Existing and projected land uses in relation to existing and projected noise sources
• Existing and proposed sensitive receptors, including: 
 
» Residential land uses
 
» Hospitals
 
» Convalescent homes
 
» Schools
 
» Churches
 
» Sensitive wildlife habitat, including the habitat of rare, threatened, or endangered species 
• Time-of-day, day-of-week, or seasonable variability of noise sources
Projections of future noise sources, noise levels, and anticipated impacts, including health impacts, upon existing and proposed 
land uses should provide information useful for guiding decisions about land use, locations of noise generating sources, and 
noise reduction mitigation measures. Mapping noise contours creates an opportunity to engage the community in a practical 
discussion about noise, and the tradeoffs between noise and other local priorities.
Mitigation Measures
Not all noise can be minimized, and there may even be areas where noise is desired. Some noise sources are inherent to a 
region, such as noise generated from farming activities in agriculture intensive areas, wildlife noise from nearby habitat, and 
noise associated with urban 
infill
 developments. Creating 
healthy communities
 includes minimizing harmful exposure to 
excessive noise. Local planning areas are encouraged to embrace the noise characteristics inherent to their region and “design 
with noise in mind” to minimize harmful exposure to excessive noise.  
There are many ways to minimize harmful exposure to excessive noise. Mitigation measures include soundproofing with 
soundproof windows and insulation, landscaping and berms, building design and setbacks, buffer areas, operating hours of 
major sources, roadway maintenance and traffic flow, quieter pavement strategies, and other techniques. 
Noise mitigation measures are not one-size-fits-all solutions: some noise mitigation measures are better suited for some 
communities than others. For example, while sound walls may be a fitting mitigation measure for a rural area, they may not be 
the best solution for urban infill areas, because they impair community connectivity. Increased building setback zones or buffer 
zones are likely not appropriate in more urban areas where land is limited. In areas where available land is limited, alternative 
mitigation measures should be employed. The noise element should be flexible and consider the different needs of various 
communities to determine the best measures to minimize exposure to excessive noise. 
Caltrans administers several freeway noise control programs. In general, these are applied to residential and school uses 
that existed before a freeway was constructed. For instance, the 
New Construction or Reconstruction and Community Noise 
Abatement programs
 provide for installation of noise attenuating walls. In addition, the 
School Noise Abatement Program
 funds 

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