N.J. Admin. Code § 7:29-2.9

Current through Register Vol. 56, No. 21, November 4, 2024

Section 7:29-2.9 - Procedure

(a) Calibration of Sound Measuring Equipment: When a meter zero adjust screw is accessible from outside the sound measuring equipment, then prior to making sound level measurements, the investigator shall zero adjust in accordance with the manufacturer's instructions. If the zero adjust screw of the equipment is not readily accessible, and if the investigator observes that the meter zero adjust is defective, the equipment shall be taken out of service until repaired. Before and after making a set of sound level measurements, the investigator shall check, and if warranted, adjust the sound level meter calibration at the level specified by the sound level calibrator used. When a multi-frequency calibrator is used, it shall be set at 1000 Hertz. The procedures below shall be followed before and after each set of measurements:

1. Turn on the sound level meter and allow it to warm-up as specified by the manufacturer--usually three to five minutes;

2. Check the condition of the sound level meter battery and replace if necessary;

3. Set the sound level meter range or attenuator setting to the appropriate level (most calibrators produce sound levels in the range of 94 to 124 dB);

4. Set the sound level meter for slow response and set the sound level meter weighting switch to the appropriate position in accordance with the manufacturer's instructions for the sound level calibrator to be used;

5. Test the calibrator batteries and replace them if necessary;

6. Allow the calibrator to warm-up if necessary as specified by the manufacturer;

7. Place the calibrator on the microphone gently to prevent damage to the microphone diaphragm; and

8. Adjust the sound level meter using the calibration (sensitivity or amplifier gain) adjustment until the meter reads the calibrator output.

(b) Measurement: After calibrating the sound level meter, switch to the appropriate weighting position and place the wind screen over the microphone. The appropriate weighting position is "A" for measurement of continuous or impulse sound, and "flat" or "ext. Filter" for octave band measurements. The meter is now ready for measuring the sound level.

1. Total sound level is measured as follows:

i. Position the microphone at the point at which the sound is to be measured.

ii. During sound level measurements, the sound level meter microphone is to be mounted on a tripod or held at arm's length, at a minimum of three feet (0.9 meter) above ground level, and pointed at the proper angle to an imaginary line from the sound source to the microphone. The proper angle is specified by the manufacturer, according to the microphone characteristics.

iii. When measuring continuous sound, the measuring device shall be set for "A" weighting, "slow" meter response, and the range switch shall be set to that range in which the meter display reads nearest to the maximum end of the scale. When the measured sound is variable, causing the meter display to fluctuate, record both the minimum and maximum readings, for example, 66-69 dBA, indicating that the reading was not less than 66 nor more than 69, during the measurement. When selecting the proper range setting for making the measurement, do not include extraneous sounds.

iv. When octave band measurements are made, the sound from the source must be constant in level and in character. Record the maximum and minimum readings in dB. Use "flat" response or "ext. Filter" setting as appropriate to the instrument. (Do not use "A" scale.) If level variations exceed plus or minus 2 dB in the bands containing the principal source frequencies, discontinue the measurement. The octave band level shall be used as a supplement to "A" weighted level measurements.

v. To measure impulse noise, the investigator shall set the meter for "A" weighting. The investigator may use either the fast or impulse setting, and may employ the "hold" setting. If the investigator is not employing the "hold" setting, he or she should report the maximum sound level displayed on the meter for a representative number of impulses. If the "hold" setting is employed after measuring an impulse, press the reset button to prepare for measurement of the next impulse. If the impulses follow each other rapidly as for example in a fusillade, it is not necessary to measure every impulse. In such a case, measure as many impulses as feasible, estimate the number of impulses occurring, and the time period during which they occur.

vi. While making sound level measurements, observe whether the meter reading is increased by extraneous sound sources such as passing vehicles, aircraft flying overhead, barking dogs, etc. In such cases, postpone the sound level measurement until the extraneous sound has abated. This shall not apply, however, if the source of the extraneous sound is located on the facility under investigation.

vii. There are instances in which the sound propagation from a source is such that the sound level varies significantly with altitude. In such cases, connect the sound level meter to its microphone by a long cable and, after calibrating, elevate the microphone with a long pole or other means to measure the sound level at different altitudes.

viii. Continue the test over a period of time sufficient to ensure that the sound levels measured are typical of the source under observation but in no event should the duration of the test be less than 10 minutes, unless the duration or duty cycle of the sound source under observation is less than 10 minutes.

ix. No less frequently than at one hour intervals during the investigation, and again at the conclusion of measurement, calibrate the sound level meter, check the condition of the batteries, measure the wind speed, and record the results for inclusion in the Noise Measurement Report. If the sound level meter has drifted more than 0.5 dB off calibration, or if the sound level meter battery check procedure indicates that the battery charge is too low, or if the wind speed has increased to greater than 12 miles per hour (5.4 meters per second), then measurements taken since the previous calibration check shall be considered invalid. A meter with an electronic display showing a "low battery" indication may continue to be operated for the duration specified in the manufacturer's manual without invalidating the previous readings, if a subsequent calibration check is satisfactory. Wind gusts over 12 miles per hour (5.4 meters per second) that begin after at least one hour of measurements shall not invalidate measurements already collected.

2. Neighborhood residual sound is measured as follows:

i. When the sound from the source under investigation can be discontinued, the neighborhood residual sound shall be measured at the same location at which the total sound was measured. When the sound under investigation cannot be reasonably discontinued, the neighborhood residual sound may be measured at an alternative location, in accordance with the following procedure:

(1) The alternative location should be as close as feasible to the original sound measurement location, but so located that the sound from the source has as little effect as possible on the neighborhood residual sound measurement. Even if the source sound is audible or is sufficient to raise the sound level above that which would be measured were it inaudible at the alternative location, the reading is sufficient for the purpose of this procedure.

(2) The alternative location chosen must be such that buildings in the vicinity are similar in size and distribution, the local topography is similar in character to the location of the affected property where the total sound was measured.

(3) Traffic conditions at the time of neighborhood residual sound measurement must be similar to those at the location of the affected property where the total sound was measured.

N.J. Admin. Code § 7:29-2.9

Amended by R.2007 d.227, effective 8/6/2007.
See: 38 N.J.R. 2774(a), 39 N.J.R. 3372(a).
In (a)7, inserted "and" at the end; in (a)8, substituted a period for a semicolon at the end; deleted (a)9; in (b)1iii, substituted "display" for "needle" two times and "for example," for "e.g."; rewrote (b)1v; in (b)1viii, inserted ", unless the duration or duty cycle of the sound source under observation is less than 10 minutes"; and rewrote (b)1ix.