BAC SP #2 Sky Posse Palo Alto The Basics Of Noise Metrics 0001

Environmental sound is measured in dBA (Decibels, A-weighted), an international metric that is commonly used to assess environmental noise exposure ' Decibels (dB) measure the sound energy. ' The A-weighted scale adjusts the frequency content of the sound to approximate how noise is perceived on the human ear. ' As a rule of thumb, a 10 dB increase is perceived as about twice as loud. Typical Outdoor Sound Measured on a Quiet Suburban Street (Source: EPA1) Single event noise metrics Average noise metrics • Lmax: Maximum noise level of one noise ' Leq (Equivalent Noise Level): average sound event. level over a given time period. ' SEL (Sound Exposure Level): total A- ' LAeq (also written as dBA Leq): same as Leq weighted energy of a noise event over its but A-weighted to approximate how the entire duration but compressed to one human ear would perceive the noise. second. SEL will typically be higher than ' DNL (Day-Night Average Sound Level) Lmax. called Ldn '24-hour time weighted energy average noise level '10 dB penalty between IC)pm to 7am to account for the higher sensitivity to noise at night due to lower background noise • CNEL (Community Noise Equivalent Level): same as DNL but adds a 5 dB penalty between 7pm and IC)pm. The FAA accepts the use of CNEL by California to assess noise effects.1 nU SHP•+ eden f:+ li t:_1 ++ q: rJ) Sky Posse Palo Alto skypossepaloalto.org The Basics of Noise Metrics q + ’ L ' eft…

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Call to order – Roll Call – Quorum Established – Land Acknowledgement We would like to acknowledge that our Agency operates in four present-day counties, which are the traditional lands of the Coast Salish people, past and present. This acknowledgement does not take the place of authentic relationships with indigenous communities in our jurisdiction and [...]