The following words, terms and phrases, when used in this section 13-15, shall have the meanings ascribed to them in this section, except where the context clearly indicates a different meaning:
"A" BAND LEVEL: The total sound level of all noise as measured with a sound level meter using A-weighting network. The unit is the dB(A).
AMBIENT NOISE: The all encompassing noise associated with a given environment, being usually a composite of sounds from many sources, near and far. For the purpose of this section 13-15, "ambient noise" level is the level obtained when the noise level is averaged over a period of fifteen (15) minutes without inclusion of noise from isolated identifiable sources, at the location and time of day near that at which a comparison is to be made. Averaging may be done by instrumental analysis in accordance with American national standards S13-1971, or may be done manually as follows:
A. Observe a sound level meter for five (5) seconds and record the best estimate of central tendency of the indicator needle, and the highest and lowest indications.
B. Repeat the observations as many times as necessary to ensure that observations are made at the beginning and the end of the fifteen (15) minute averaging period and that there are at least as many additional observations as there are decibels between the highest high indication and the lowest low indication.
C. Calculate the arithmetical average of the observed central tendency indications.
DECIBEL: A sound pressure that is twenty (20) times the logarithm to the base ten (10) of the ratio of the pressure of sound to the reference pressure, 2 x 10-5 Newton/meter2.
EMERGENCY WORK: Work made necessary to restore property to a safe condition following a public calamity or work required to protect the health, safety or welfare of persons or property or work by private or public utilities when restoring utility service.
FREQUENCY: "Frequency" of a function periodic in time shall mean the reciprocal of the primitive period. The unit is the hertz and shall be specified.
IMPULSE NOISE: A noise of short duration, usually less than one second, with an abrupt onset and rapid decay.
MICROBAR: A unit of pressure commonly used in acoustics and is equal to one dyne per square centimeter.
MOTOR VEHICLES: Any self-propelled vehicle operated within the city, including, but not limited to, licensed or unlicensed vehicles, automobiles, minibikes, go-carts and motorcycles.
PERIOD: "Period" of a periodic quantity shall mean the smallest increment of time for which the function repeats itself.
PERIODIC QUANTITY: Oscillating quantity, the values of which recur for equal increments of time.
PURE TONE NOISE: Any noise which is distinctly audible as a single pitch (frequency) or set of pitches as determined by the enforcement officer.
SOUND LEVEL: "Sound level" (noise level), in decibels (dB), is the sound measured with the A-weighting and slow response by a sound level meter.
SOUND LEVEL METER: An instrument including a microphone, an amplifier, an output meter, and frequency weighting networks for the measurement of sound levels which satisfies the pertinent requirements in American standard specifications for sound level meters S1.4-1971 or the most recent revision thereof. (Ord. 00-502 § 2, 12-11-2000; Ord. 07-704 § 1, 7-23-2007)