The following standards shall apply to the measurement of sound levels pursuant to sections
A. Insofar as practicable, sound will be measured while the source under investigation is operating at normal, routine conditions and, as necessary, at other conditions, including, but not limited to, design, maximum, and fluctuating rates.
B. When a noise source can be identified and measured in more than one type of premises, the limits of the most restrictive use shall apply at the property line between different premises types.
C. All tests shall be conducted in accordance with the following procedures:
1. The enforcement officer shall, to the extent practicable, identify all sources contributing sound to the point of measurement.
2. Measurements shall be taken at or within the property line of the receiving property; provided that whenever it is impossible or impractical to measure at the property line, a greater distance from the noise source shall be used to determine compliance with this chapter.
3. The Sound Level Meter (SLM) must be calibrated in accordance with manufacturer specifications.
4. No outdoor measurements shall be taken:
a. During periods when wind speeds (including gusts) exceed fifteen miles per hour (15 mph);
b. Without a windscreen, recommended by the SLM manufacturer, properly attached to the SLM;
c. Under any condition that allows the SLM to become wet (e.g., rain, snow, or condensation); or
d. When the ambient temperature is out of the range of the tolerance of the SLM.
D. The report for each measurement shall include:
1. The date, day of the week, and times at which measurements are taken;
2. The times of calibration;
3. The weather conditions;
4. The identification of all monitoring equipment by manufacturer, model number, and serial number;
5. The normal operating cycle of the sources in question with a description of the sources;
6. The ambient sound level, in dBA, with the sources in question operating;
7. The background sound level, in dBA, without the sources in question operating; and
8. A sketch of the measurement site, including measurement locations and relevant distances, containing sufficient information for another investigator to repeat the measurements under similar conditions.
E. Prior to taking measurements the enforcement officer shall explore the vicinity of the source in question to identify any other sound sources that could affect measurements, to establish the approximate location and character of the principal sound source, and to select suitable locations from which to measure the sound from the source in question.
F. When measuring continuous sound, or sound that is sustained for more than one second at a time, the SLM shall be set for A-weighting, slow meter response speed, and the range (if the SLM is designed to read levels over different ranges of sound pressure levels (SPL) shall be set to that range in which the meter reads closest to the maximum end of the scale. When the measured sound level is variable or fluctuating over a range greater than +3 dBA, using the slow meter response speed, the fast meter response speed shall be used. In either case, both the minimum and maximum readings shall be recorded to indicate the range of monitored values.
G. The SLM shall be placed at a minimum height of three feet (3') above the ground or from any reflective surface. When handheld, the microphone shall be held at arm's length and pointed at the source at the angle recommended by the SLM manufacturer.
H. If extraneous sound sources, such as aircraft flyovers or barking dogs, that are unrelated to the measurements increase the monitored sound levels, the measurements should be postponed until these extraneous sounds have become of such a level as not to increase the monitored sound levels of interest.
I. The monitoring session should last for a period of time sufficient to ensure that the sound levels measured are typical of the source in question.
J. The background sound levels shall be subtracted from the measured sound levels of the source of interest by using table 1 of this section to determine the sound levels from the source of interest alone. If the ambient sound level is less than 3 dBA higher than the background sound level, the source level cannot be derived, and a violation of this chapter cannot be substantiated.
TABLE 1 CORRECTION FOR BACKGROUND LEVELS (In dBA) | |
Difference Between Ambient And Background Sound Levels | Correction Factor To Be Subtracted From Ambient Level For Source Level |
3 | 3 |
4, 5 | 2 |
6 - 9 | 1 |
10 or more | 0 |
(Ord. 2022-09, 7-12-2022)