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7.B. - Page 83 Redwood City Chapter 4.Environmental Impact Analysis Policy PS-13.5: Limit the hours of operation at all noise generation sources that are adjacent to noise sensitive areas,wherever practical. Policy PS-13.6: Require all exterior noise sources (construction operations,air compressors, pumps,fans,and leaf blowers) to use available noise suppressions devices and techniques to bring exterior noise down to acceptable levels that are compatible with adjacent land uses. Policy PS-13.8: Implement appropriate standard construction noise controls for all construction projects. Environmental Setting Noise Terminology Below are brief definitions of noise terminology used in this section. • Sound. Sound is caused by vibration that produces pressure waves that travel outward from the source of the disturbance.The human perception of sound varies according to the characteristics of the sound waves (e.g.,period,amplitude,frequency,speed,and wavelength) and the characteristics of the media through which the sound travels (e.g.,air,water,and solids). • Noise. Noise is defined as unwanted sound that adversely affects any given receiver location.In general,sound waves travel away from a ground level noise source in a hemispherical pattern. As a result,the energy contained in a sound wave is spread over an increasing area as it travels away from the source.This results in a decrease in loudness at greater distances from the noise source. • Decibel (dB).Sound level meters measure the air pressure fluctuations caused by sound waves, with separate measurements made for different sound frequency ranges.The dB scale used to describe sound is a logarithmic scale,which accounts for the large range of audible sound intensities. • A-Weighted Decibel (dBA). Most sounds consist of a broad range of sound frequencies.The dBA scale is a measure of sound intensity that is weighted to take into account the human perception of different frequencies of sound. • Equivalent Sound Level (Le9). Leq represents an average of the sound energy occurring over a specified period. In effect,Leq is the steady-state sound level that would contain the same acoustical energy as the time-varying sound that actually occurs during the monitoring period. The 1-hour A-weighted equivalent sound level (Leq 1h) is the energy average of A-weighted sound levels occurring during a 1-hour period. • Maximum and Minimum Sound Levels (Lm�,Lmin).The maximum (LmaX) and minimum (Lm;,,) sound levels measured during a monitoring period. • Community Noise Equivalent Level (CNEL).The energy average of the A-weighted sound levels occurring during a 24-hour period,with a 5-dB penalty added to sound levels between 7:00 p.m.and 10:00 p.m.and a 10-dB penalty added to sound levels between 10:00 p.m.and 7:00 a.m. Addendum No.2 to the Environmental Impact Report for 4 38 September 2012 the Redwood City Costco Wholesale Project ICF 00154.12