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For the purposes of this chapter, the following definitions shall apply:
A-SCALE: The A-scale level (dB(A) or dBA) is expressed in decibels, and shall be the sound pressure level which is frequency weighted in accordance with an A-weighting network.
dB(A) LEVEL: The total sound level of all noise, as measured with a sound level meter using the A-weighting network. The unit is the decibel.
DECIBEL (dB): A logarithmic unit of amplitude which denotes the ratio of two (2) quantities.
SOUND LEVEL METER: An instrument, including a microphone, an amplifier, an output meter, and frequency weighting networks for the measure of noise and sound pressure levels in a specified manner.
SOUND PRESSURE LEVEL (SPL, Lp): Is expressed in decibels, and shall be twenty (20) times the logarithm to the base ten (10) of the ratio of the effective sound pressure to the reference sound pressure. The effective sound pressure shall be the root mean square of the instantaneous sound pressure. The reference pressure shall be twenty (20) microneutrons per meter squared. (Ord. 1231-72, 1972)