Draft Environmental Impact Report - California Off Highway Vehicle ...

3.3 Noise
nonauditory health effects remains a subject of considerable research, with no definitive
conclusions.
The degree to which noise results in annoyance and interference is highly subjective and may be
influenced by several nonacoustic factors. The number and effect of these nonacoustic
environmental and physical factors vary depending on individual characteristics of the noise
environment such as sensitivity, level of activity, location, time of day, and length of exposure. One
key aspect in the prediction of human response to new noise environments is the individual level
of adaptation to an existing noise environment. The greater the change in the noise levels that are
attributed to a new noise source, relative to the environment an individual has become
accustomed to, the less tolerable the new noise source will be to the new noise source.
With respect to how humans perceive and react to changes in noise levels, a 1‐dBA increase is
imperceptible, a 3‐dBA increase is barely perceptible, a 6‐dBA increase is clearly noticeable, and a
10‐dBA increase is subjectively perceived as approximately twice as loud (Egan 1988:21). These
subjective reactions to changes in noise levels were developed on the basis of test subjects’
reactions to changes in the levels of steady‐state pure tones or broad‐band noise and to changes in
levels of a given noise source. It is probably most applicable to noise levels in the range of 50 dBA
to 70 dBA, as this is the usual range of voice and interior noise levels. Depending on the existing
noise environment and the new sources added to it, an increase in noise level of 3 dBA or more is
typically considered perceptible in terms of the existing noise environment.
Fundamental Noise Control Options
Any noise problem may be considered as being composed of three basic elements: the noise
source, a transmission path, and a receptor. The appropriate acoustical treatment for a given
project should consider the nature of the noise source and the sensitivity of the receptor. The
problem should be defined in terms of appropriate criteria (Ldn, Leq, or Lmax); the location of the
sensitive receptor (inside or outside); and the time that the problem occurs (daytime or
nighttime). Noise control techniques should then be selected to provide an acceptable noise
environment for the receiving property while remaining consistent with local aesthetic standards
and practical structural and economic limits. Fundamental noise control options are described
below.
Use of Setbacks
Noise exposure may be reduced by increasing the distance between the noise source and the
receiving use. Setback areas can take the form of, for example, open space, frontage roads,
recreational areas, and storage yards. The available noise attenuation from this technique is
limited by the characteristics of the noise source, but is generally about 4–6 dBA.
Clay Pit State Vehicular Recreation Area
Draft EIR 3.3-5 February 2012