The following words or phrases as used in this Chapter shall have the following meanings:
A-weighted sound pressure level.
The sound pressure level which has been filtered or weighted to quantitatively reduce the effect of low frequency noise. It was designed to approximate the response of the human ear to sound. A-weighted sound pressure level is measured in decibels with a standard sound level meter which contains the “A” weighting network. A-weighted decibels are abbreviated dBA. Relevant standards are defined by the American National Standards Institute Specification for Sound Level Meters (S1.4-1971).
Community Noise Equivalent Level.
The CNEL is the annual average (on an energy basis) noise level measured in A-weighted sound pressure level for a twenty-four hour period with different weighting factors for the noise levels occurring during the day, evening, and nighttime periods. CNEL is defined by California Division of Aeronautics, “Noise Standards for California Airports,” California Administrative Code Chapter 9, Title 4 (Register 70, No. 48, November 28, 1970).
Single Event Noise Exposure Level.
SENEL is the time-integrated A-weighted sound pressure level of a single aircraft flyover (which exceeds a threshold noise level) which is expressed by the level of an equivalent one-second duration reference signal. The threshold level at the Airport shall be at least sixty-five dBA. SENEL provides a measure which quantifies the effect of duration and magnitude for a single event measured above a specified threshold. SENEL is defined by California Division of Aeronautics, “Noise Standards for California Airports,” California Administrative Code Chapter 9, Title 4 (Register 70, No. 48, November 28, 1970).
Sound pressure level.
The sound pressure level of a sound is twenty times the logarithm to the base ten of the ratio of the measured root mean square (RMS) value of the sound pressure to a reference sound pressure. Measurement units are decibels (dB). The reference pressure is twenty micro pascals.
[SPL 20 = Log10 (P measured divided by P reference)]
Traffic pattern.
An approximately rectangular flight track designed to provide for an organized flow of local traffic around the Airport in which the runway centerline forms one part of one of the longer legs of the rectangle. The traffic pattern shall be established by the Federal Aviation Administration in cooperation with the City.
(Prior code § 10150; added by Ord. No. 1326CCS, adopted 1/22/85)