For the purposes of this chapter, certain words and phrases used herein are defined as follows, and if not defined herein, shall be in conformance with applicable American National Standards Institute publication, including but not limited to ANSI 1-1960 or those from its successor publications or bodies: (1984 Code §§ 23A-3, 23A-10)
A-WEIGHTED SOUND LEVEL: The sound level as measured with a sound level meter using the A-weighting network. The standard notation is dB(A) or dBA.
AMBIENT SOUND PRESSURE LEVEL: The sound pressure level of the all encompassing noise associated with a given environment usually a composite of sounds from many sources. It is also the A-weighted sound pressure level exceeded ninety percent (90%) of the time based on a measurement period of not less than ten (10) minutes nor more than thirty (30) minutes.
CONTINUOUS SOUND: Any sound which exists, essentially without interruption, for a period of ten (10) minutes or more.
CYCLICALLY VARYING NOISE: Any sound which varies in sound level such that the same level is obtained repetitively at reasonably uniform intervals of time.
DECIBEL (dB): Logarithmic and dimensionless unit of measure used in describing the amplitude of sound.
DEVICE: Any mechanism which is intended to produce or which actually produces noise when operated or handled.
DYNAMIC BRAKING DEVICE: (Commonly referred to as Jacob's brake). A device used primarily on trucks for the conversion of the engine from an internal combustion engine to an air compressor for the purpose of braking without the use of wheel brakes.
EMERGENCY VEHICLE: A motor vehicle used in response to a public calamity or to protect persons or property from an imminent exposure to danger.
EMERGENCY WORK: Work made necessary to restore property or a public utility to a safe condition following a public calamity or work required to protect persons or property from an eminent exposure to danger.
IMPULSIVE NOISE: A noise containing excursions, usually less than one second, of sound levels of twenty (20) dB(A) or more over the ambient sound level using the fast meter characteristic.
MOTOR VEHICLE: Any vehicle which is self-propelled by mechanical power, including but not limited to passenger cars, trucks, truck trailers, semitrailers, campers, motorcycles, minibikes, go-carts, mopeds and racing vehicles.
MUFFLER: An apparatus consisting of a series of chambers of baffle plates designed for the purpose of transmitting gases while reducing sound emanating from such apparatus.
NOISE: Any sound which is unwanted or which causes or tends to cause an adverse psychological or physiological effect on human beings.
NOISE DISTURBANCE: Any sound which annoys or disturbs reasonable persons with normal sensitivities or which injures or endangers the comfort, repose, health, hearing, peace or safety of other persons.
PERCENTILE SOUND PRESSURE LEVEL: Tenth Percentile Noise Level (L10): The A-weighted sound pressure level that is exceeded ten percent (10%) of the time in any measurement period (such as the level that is exceeded for 1 minute in a 10 minute period).
Ninetieth Percentile Noise Level (L90): The A-weighted sound pressure level that is exceeded ninety percent (90%) of the time in any measurement period (such as the level that is exceeded for 9 minutes in a 10 minute period).
PERSON: Any human being, firm, association, organization, partnership, business, trust, corporation, company, contractor, supplier, installer, user, owner or operator, including any municipal corporation or its officers or employees.
PLAINLY AUDIBLE NOISE: Any noise for which the information content of that noise is unambiguously transferred to the listener, such as but not limited to understanding of spoken speech, comprehension of whether a voice is raised or normal or comprehension of musical rhythms.
PROPERTY BOUNDARY: An imaginary line exterior to any enclosed structure, at the ground surface, and its vertical extension, which separates the real property owned by one person from that owned by another person.
PUBLIC RIGHT OF WAY: Any street, avenue, boulevard, highway or alley or similar place which is owned or controlled by a public governmental entity.
PURE TONE: Any sound which can be distinctly heard as a single pitch or a set of single pitches. For the purposes of measurement, a "pure tone" shall exist if the one-third (1/3) octave band sound pressure level in the bank with the tone exceeds the arithmetic average of the sound pressure levels of the two (2) contiguous one-third (1/3) octave bands by five (5) dB for center frequencies of five hundred (500) Hz and above, by eight (8) dB for center frequencies between one hundred sixty (160) and four hundred (400) Hz and by fifteen (15) dB for center frequencies less than or equal to one hundred twenty five (125) Hz.
REPETITIVE IMPULSIVE NOISE: Any noise which is composed of impulsive noises that are repeated at sufficiently slow rates such that a sound level meter set at "fast" meter characteristic will show changes in sound pressure level greater than ten (10) dB(A).
SOUND: Mechanical energy transmitted by a cyclic series of compressions and rarefaction of molecules of that material or materials through which it passes.
SOUND LEVEL METER: An instrument, including a microphone, amplifier, RMS detector and integrator or time averager, output meter and/or visual display and weighting networks, used to measure sound levels. The sound level meter shall conform as a minimum to the requirements of ANSI S 1.4 - 1971 type 2 or its successor publication and shall be set to an A-weighted response. An acoustical calibrator accurate to within plus or minus one decibel shall be used to verify the before and after calibration of the sound level meter on each day noise measurements are taken.
SOUND PRESSURE: The instantaneous difference between the actual pressure and the average or barometric pressure at a given point in space, as produced by sound.
SOUND PRESSURE LEVEL (Lp or SPL): Twenty (20) times the logarithm to the base ten (10) of the ratio of the RMS sound pressure to the reference pressure of twenty (20) micropascals.
STATIONARY NOISE SOURCE: Any device, fixed or movable, including motor vehicles, which is located or used on property other than a public right of way.
STEADY NOISE: A sound pressure level which remains essentially constant during the period of observation, i.e., does not vary more than six (6) dB(A) when measured with the "slow" meter characteristic of a sound level meter.
USE DISTRICT: Those districts established by the Mitchell zoning ordinance 1 . (1984 Code § 23A-11)



1. Title 10 of this code.