7.30.020 DEFINITIONS.

(a) "Sound level," expressed in decibels (dB), means a logarithmic indication of the ratio between the acoustic energy present at a given location and the lowest amount of acoustic energy audible to sensitive human ears and weighted by frequency to account for characteristics of human hearing, as given in the American National Standards Institute Standard S1.1, "Acoustic Terminology," paragraph 2.9, or successor reference. All references to dB in this chapter utilize the A-level weighting scale.

(b) "Noise level" means the maximum sound level by a source or group of sources as measured with a precision sound level meter, conforming to the American National Standards Institute Standard S1.4-1983, for Type 1 meters (or successor reference), using the "A" weighted, slow sound pressure level scale, five feet above the ground.

(c) "Ambient" means the average sound level during a six-minute period as measured with a precision sound level meter, using slow response and "A" weighting. The sound level shall be determined with the noise source at issue silent and in the same location as the measurement of the noise level of the source or sources at issue. If for any reason the alleged offending noise source cannot be shut down, the ambient noise must be estimated by performing a measurement in the same general area of the source but at a sufficient distance that the noise from the source is at least 10 dB below the ambient so that only the ambient level is measured. If the difference between the ambient and the noise source is five to nine dB, then the level of the ambient itself can be determined by subtracting a one dB correction to account for the contribution of the source.

(d) "Vehicle" means any device by which any person or property may be propelled, moved or drawn upon a highway or street.

(e) "Property plane" means a vertical plane including the property line, which determines the property boundaries in space.

(f) "Emergencies" means essential activities necessary to restore, preserve, protect or save lives or properties from imminent danger or loss or harm.