Environmental Impact Statement - Sonoma Land Trust

California Department of Fish and Game
U.S. Fish and Wildlife Service
Section 3.12. Noise
• Ambient Noise—the composite of noise from all sources near and far in a
given environment exclusive of particular noise sources to be measured.
• Decibel, dB—a unitless measure of sound on a logarithmic scale which
indicates the squared ratio of sound pressure amplitude to a reference sound
pressure amplitude. The reference pressure is 20 micro-Pascals.
• A-Weighted Decibel, dBA—an overall frequency-weighted sound level in
decibels which approximates the frequency response of the human ear.
• Equivalent Sound Level, L eq —the equivalent steady state sound or
vibration level which in a stated period of time would contain the same
acoustical or vibration energy.
• Percentile Exceeded Sound Level, L xx —the sound level exceeded a
specified percentage of the measurement duration. For L 10 is the sound level
exceeded 10 percent of the time and L 90 is the sound level exceeded 90
percent of the time.
• Day-Night Level, L dn —the energy average of the A-weighted sound levels
occurring during a 24-hour period, with 10 dB added to the A-weighted
sound levels occurring during the period from 10 p.m. to 7 a.m.
In general, human sound perception is such that a change in sound level of 3dB is
generally perceived as being just noticeable, a change of 5 dB is clearly
noticeable, and a change of 10 dB is perceived as a doubling or halving of sound
level.
Noise-Sensitive Land Uses
Noise-sensitive land uses are generally defined as locations where people reside
or where the presence of unwanted sound could adversely affect the use of the
land. Noise-sensitive land uses typically include residences, hospitals, schools,
guest lodging, libraries, and certain types of recreational uses. Noise sensitive
land uses in the project area include hiking areas along existing segments of the
Bay Trail that are used for wildlife viewing and enjoyment of natural
surroundings. The Bay Trail meets and ends at Reclamation Road at the western
project area boundary. This portion of the trail represents a noise-sensitive land
use. The Bay Trail also roughly parallels the eastern boundary of the project area
on the opposite side of Tolay Creek; however, the trail is located below an
existing levee along the banks of Tolay Creek that precludes views of the site and
substantially buffers trail users from noises emanating from the project site.
Therefore, this segment of the Bay Trail is not considered a noise-sensitive land
use for the purpose of this analysis.
Noise-sensitive land uses in the project area also include three 10-acre residential
parcels within the Paradise Vineyards area, located north of the SMART rail line
and west of the USFWS refuge headquarters where the rail line turns to the north.
Two of these residences are within 500 feet of the Project boundary.
Sears Point Wetland and Watershed Restoration
Project Final Environmental Impact
Report/Environmental Impact Statement
3.12-2
April 2012