42-21 Performance Standards Regulating Noise
For the purposes of this Section, the following terms are defined:
A "decibel" is a unit of measurement of the intensity of sound (the sound pressure level).
Impact noise analyzer
An "impact noise analyzer" is an instrument used in conjunction with the sound level meter to measure the peak intensities of short duration sounds.
An "octave band" is one of a series of eight bands which cover the normal range of frequencies included in sound measurements. Such octave bands serve to define the sound in terms of its pitch components.
Octave band analyzer
An "octave band analyzer" is an instrument used in conjunction with a sound level meter to measure sound in each of eight octave bands.
Sound level meter
A "sound level meter" is an instrument standardized by the American Standards Association, which is used for measurement of the intensity of sound and is calibrated in decibels.
For the purpose of measuring the intensity or frequency of sound, the sound level meter, the octave band analyzer, and the impact noise analyzer shall be employed.
The "C" network and the "slow" meter response of the sound level meter shall be used. Sounds of short duration, as from forge hammers, punch presses, and metal shears, which cannot be measured accurately with the sound level meter, shall be measured with the impact noise analyzer as manufactured by the General Radio Company, or its equivalent, in order to determine the peak value of the impact. For sounds so measured, the sound pressure levels set forth in Section 42-213 (Maximum permitted decibel levels) may be increased by six decibels.
In all Manufacturing Districts, the sound pressure level resulting from any activity, whether open or enclosed, shall not exceed, at any point on or beyond any lot line, the maximum permitted decibel levels for the designated octave band as set forth in the following table for the district indicated.
In the enforcement of this regulation, sounds produced by the operation of motor vehicles or other transportation facilities shall not be included in determining the maximum permitted decibel levels.
MAXIMUM PERMITTED SOUND PRESSURE LEVEL
(cycles per second)
20 to 75
75 to 150
150 to 300
300 to 600
600 to 1,200
1,200 to 2,400
2,400 to 4,800
Whenever a Manufacturing District adjoins a Residence District, at any point at the district boundary or within the Residence District, the maximum permitted decibel levels in all octave bands shall be reduced by six decibels from the maximum levels set forth in the table in Section 42-213 (Maximum permitted decibel levels).