Sec. 10-53. - Decibel provisions.

(a)

Definitions. For the purpose of this section, certain words and phrases used in this chapter are defined as follows:

A band level is the total sound level of all noise as measured with a sound level meter using the A weighing network. The unit of measurement is the dB(A).

Ambient noise is the all-encompassing noise associated with a given environment, being usually a composite of sounds from many sources, near and far.

Band pressure level of sound for a specified frequency band is the sound pressure level for the sound contained within the restricted band. The reference pressure must be specified.

Bel is a unit of level when the base of logarithm is ten. Use of the bel is restricted to levels of quantities proportional to power.

Cycle is the complete sequence of values of a periodic quantity that occur during a period.

Decibel is one-tenth of a bel and is a unit of level when the base of the logarithm is the tenth root of ten, and the quantities concerned are proportional to power.

Emergency work is work made necessary to restore property to a safe condition following a public calamity or work required to protect persons or property from an imminent exposure to danger.

Frequency of a function periodic in time is the reciprocal of the primitive period. The unit is the cycle per unit and must be specified.

Microbar is a unit of pressure commonly used in acoustics and is equal to one dyne per square centimeter.

Period of a periodic quantity is the smallest increment of time for which the function repeats itself.

Periodic quantity is an oscillating quantity, the values of which recur for equal increments of time.

Person is any person or a person's firm, association, copartnership, joint venture, corporation or any entity public or private in nature.

Sound analyzer is a device for measuring the band pressure level or pressure spectrum level of a sound as a function of frequency.

Sound-level meter is an instrument including a microphone, an amplifier, an output meter, and frequency weighting networks for the measurement of noise and sound levels in a specified manner.

Sound pressure level in decibels of sound, is 20 times the logarithm to the base ten of the ratio of the pressure of this sound to the reference pressure, which reference pressure must be explicitly stated.

Spectrum is a function of time and is a description of its resolution into components, each of different frequency and usually of different amplitude and phase. It is also used to signify continuous range of components each of different frequency and usually of different amplitude and phase, and it is also used to signify continuous range of components usually wide in extent within which waves have some specified characteristics such as audio-frequency spectrum. It is also applied to functions of variables other than time.

All technical definitions are in accordance with American Standards S1.1-1960 entitled Acoustical Terminology.

(b)

General provision: Tests for unlawful noise. The standards which shall be considered in determining whether a violation of section 10-51 exists shall include, but shall not be limited to, the following:

(1)

The volume of the noise;

(2)

The intensity of the noise;

(3)

Whether the nature of the noise is usual or unusual;

(4)

Whether the origin of the noise is natural or unnatural;

(5)

The volume and intensity of the background noise, if any;

(6)

The proximity of the noise to residential sleeping facilities;

(7)

The nature and zoning of the area within which the noise emanates;

(8)

The density of inhabitation of the area within which the noise emanates;

(9)

The time of the day or night the noise occurs;

(10)

The duration of the noise;

(11)

Whether the noise is recurrent, intermittent or constant;

(12)

Whether the noise is produced by a commercial or noncommercial activity.

(c)

Classification of use districts: Residential, manufacturing, commercial. It is unlawful to directly or indirectly cause a sound or noise, excluding noise emanating from cars, trucks or motorcycles, from one property into another, generated within and/or projected into the boundary of a use district which exceeds either the limiting noise spectra set forth in Table I below, or exceeds the ambient noise level by more than three decibels.

(1)

Sound or noise projecting from one use district into another use district with a different noise level limit shall not exceed the limits of the district into which the noise is projected.

(2)

Measurement of noise:

a.

The measurement of sound or noise shall be made with a sound level meter and octave band analyzer meeting the standards prescribed by the American Standards Association. The instruments shall be maintained in calibration and good working order. Octave band corrections may be employed in meeting the response specification. A calibration check shall be made of the system at the time of any noise measurement. Measurements recorded shall be taken so as to provide a proper representation of the noise source. The microphone during measurement shall be positioned so as not to create any unnatural enhancement or diminution of the measured noise. A windscreen for the microphone shall be used when required. Traffic, aircraft and other transportation noise sources and other background noises shall not be considered in taking measurements except where such background noise interferes with the primary noise being measured.

b.

The slow meter response of the noise level meter shall be used in order to best determine that the average amplitude or any intermittent or repeated action including but not limited to loading and machinery operation has not exceeded the limiting noise spectra set forth in Table 1.

c.

The measurement shall be made at the property line of the property on which such noise is generated, or perceived, as appropriate five feet above ground.

d.

In the case of an elevated or directional sound or noise source, compliance with the noise limits is to be maintained at any elevation at the boundary.

_____ (3)

The limits referred to in this section shall be in accordance with Table I:

Table I

Zoning District Noise Standards

Maximum Allowable Octave Band Sound Pressure Levels Residential Residential

Industrial

Octave Band

Center

Frequency of

All Measurement

(HZ) Daytime All

Other

Times Daytime All

Other

Times Business

Any Time Industrial

Any Time

31.5 76 68 79 72 79 83

63 75 67 78 71 78 83

125 69 61 73 65 73 77

250 62 52 68 57 68 73

500 56 46 62 51 62 67

1000 50 40 56 45 56 61

2000 45 33 51 39 51 57

4000 40 28 47 34 47 53

8000 38 26 44 32 44 50

Single number

equivalent 60 dB(A) 50 dB(A) 65 dB(A) 55 dB(A) 65 dB(A) 70 dB(A)

(4)

If the noise is not smooth and continuous, one or more of the corrections in Table II shall be added to or subtracted from each of the decibel levels given in Table I of subsection (c)(3) of this section.

Table II

Type of Operation in Character Noise source operated less than 20 percent of any one-hour period; plus 5 dB(A)

Noise source operated less than 5 percent of any one-hour period; plus 10 dB(A)

Noise source operated less than one percent of any one-hour period; plus 15 dB(A)

Noise of impulsive character (hammering, etc.); minus 5

Noise of periodic character (hum, screech, etc.); minus 5.

(5)

If the noise occurs between the hours of 10:00 p.m. and 7:00 a.m. on Monday through Saturday or at any time on Sunday or holidays, seven shall be subtracted from each of the decibel levels given in Table I.

(d)

Motorized vehicles. It shall be unlawful to operate a motorized vehicle within the city limits which creates a noise or sound that exceeds the noise level limits set out in Table III:

Table III

Limiting Noise Levels for Motor Vehicles

Trucks and Buses:

Over 10,000 pounds: 87 dB(A) measured at 50-feet maximum allowable limit

93 dB(A) measured at 25-feet maximum allowable limit

Under 10,000 pounds: 80 dB(A) measured at 50-feet maximum allowable limit

86 dB(A) measured at 25-feet maximum allowable limit

Passenger cars: 78 dB(A) measured at 50-feet maximum allowable limit

84 dB(A) measured at 25-feet maximum allowable limit

Motorcycles, including other vehicles: 87 dB(A) measured at 50-feet maximum allowable limit

93 dB(A) measured at 25-feet maximum allowable limit

(e)

Measurement of noise. The measurement of sound or noise shall be made with a sound level meter and octave band analyzer meeting the standards prescribed by the American Standards Association. The instruments shall be maintained in calibration and good working order. Octave band corrections may be employed in meeting the response specification. A calibration check shall be made of the system at the time of any noise measurement. Measurements recorded shall be taken so as to provide a proper representation of the noise source. The microphone during measurement shall be positioned so as not to create any unnatural enhancement or diminution of the measured noise. A windscreen for the microphone shall be used when required. Traffic, aircraft and other transportation noise sources and other background noises shall not be considered in taking measurements except where such background noise interferes with the primary noise being measured.

(f)

Enclosed places of public entertainment.

(1)

It shall be unlawful to sustain in any enclosed place of public entertainment including but not limited to a restaurant, bar, cafe, discotheque, dancehall, any amplitude equal to or in excess of 95 dB(A) sustained for more than 30 seconds.

(2)

Such sound or noise is to be measured by a sound level meter approved by the American Standards Association from any area to which the public is invited within any enclosed place of public entertainment.

(g)

Aircraft noises. It shall be unlawful for any person to operate or cause to be operated any type of aircraft over the city which produces noise levels exceeding 87 dB(A) within the city.

(h)

Exemptions. The following uses and activities shall be exempt from noise level regulations:

(1)

Noises of safety signals, warning devices, and emergency pressure relief valves;

(2)

Noises resulting from any authorized emergency vehicle, when responding to an emergency call or acting in time of emergency;

(3)

Noises resulting from emergency work as defined in subsection (a) of this section;

(4)

Any other noise resulting from activities of a temporary duration permitted by law and for which a license or permit has been granted by the city in accordance with subsection (i) of this section;

(5)

Any aircraft operated in conformity with, or pursuant to federal law, federal air regulations, and air traffic control instruction used pursuant to and within the duly adopted federal air regulations shall be exempt from the provisions of subsection (g) of this section as well as the other regulations of this section. Any aircraft operating under technical difficulties, in any kind of distress, under emergency orders of air traffic control or being operated pursuant to and subsequent to the declaration of an emergency under federal air regulations shall also be exempt from the provisions of subsection (g) of this section as well as the other regulations of this section.

(i)

Application for special permit. Applications for a permit for relief from the noise level designated in this article on the basis of undue hardship may be made to the city council or its duly authorized representative. Any permit granted by the city council hereunder shall contain all conditions upon which such permit has been granted and shall specify a reasonable time that the permit shall be effective. The city council or its duly authorized representative may grant the relief as applied for if it finds:

(1)

That additional time is necessary for the applicant to alter or modify his activity or operation to comply with this section; or

(2)

The activity, operation or noise source will be of temporary duration, and cannot be done in a manner that would comply with other subsections of this section; and

(3)

That no other reasonable alternative is available to the applicant.

The city council may prescribe any conditions or requirements it deems necessary to minimize adverse effects upon the community or the surrounding neighborhood.

(Rev. Ords. 1987, § 10-53; Ch. 671, §§ II, III, 6-6-17)