(a) A sound level meter shall be used for the purposes of conducting sound level measurements. An acoustical calibrator shall be used to perform a field calibration check before and after conducting sound level measurements and at least once each hour if the duration of the investigation warrants. The meter shall be adjusted to the output of the calibrator, as specified by the manufacturer. If the meter can not be adjusted to the output of the calibrator, then the meter shall be taken out of use until repaired. If the meter drifts by more than 0.5 dB between calibration checks, all measurements taken since the last valid calibration check shall be voided. The meter and calibrator shall be laboratory calibrated annually by a laboratory accredited for such calibrations by either the American Association for Laboratory Accreditation or the National Institute of Standards and Technology.
(b) Wind speed measurements shall be taken at the sound measurement location, and sound measurements shall not be conducted when the wind speed exceeds the specifications set forth by the sound meter manufacturer, or 12 MPH if unspecified. No outdoor measurements shall be conducted without a windscreen affixed to the sound meter microphone.
(c) The noise investigator shall explore the immediate vicinity of the alleged sound source and affected person, in order to: positively confirm that the alleged source is the actual source; to identify sources of ambient and extraneous sounds; and, to select suitable locations for the measurement of the Total Sound Level and the Ambient Sound Level.
(d) Total Sound Level measurements shall be conducted at or within the property lines of the affected person. The location of outdoor measurements, at the discretion of the noise enforcement officer, must represent a location on that property which would see regular use by the complainant during the day, or be within 25 feet of the residential structure at night. Indoor measurements shall be conducted pursuant to the requirements of Section 553.04. The sound level meter reading range (minimum to maximum) shall be noted during the period of observation, excluding extraneous sounds. The reported Total Sound Levels shall represent the normal and usual operations of the source under investigation for the time periods under observation.
(e) Ambient Sound Level measurements shall be conducted in such a manner as to quantify the contribution of the ambient sound sources to the location at which the Total Sound Measurements were conducted. These measurements shall be conducted at the same location at which the Total Sound Level measurements were conducted, while the source under investigation is not operating. If sound from the source under investigation can not reasonably be discontinued, then alternative measurements may be taken by one of the following methods: walking away from the sound source until the sound level drops sufficiently to calculate a Corrected Source Sound Level (below), or; behind a barrier which blocks the sound from the source under investigation, but not the sound of the ambient sound sources, or; in a similar neighborhood with a similar distribution of structures and traffic. The choice of an alternate location or time for these measurements must take into consideration the primary source(s) of ambient sound, and remain equidistant to that source (e.g., a major road) at the new measurement location when compared to the distance between these sources and the location at which the Total Sound Level measurements were conducted on the property of the affected person. The sound level meter reading range (minimum to maximum) shall be noted during the periods of observation, excluding extraneous sounds.
(f) The Corrected Source Sound Level shall be calculated by subtracting the Ambient Sound Level from the Total Sound Level, as per Table 2, below.
TABLE 2 | |
CORRECTION FOR AMBIENT SOUND LEVELS dB | |
Difference between Total Sound Level and Ambient Sound Level (TSL - ASL) in dB | Correction Factor to be Subtracted from Total Sound Level to Calculate Corrected Source Sound Level in dB |
0-2 | Source Level < Ambient Sound Level |
3 | 3 |
4, 5 | 2 |
6 - 9 | 1 |
10 or more | 0 |
Procedure for Using Table 2 Step 1: Subtract the measured Ambient Sound Level from the measured Total Sound Level.Step 2: Refer to Table II to determine the correction factor for the difference calculated in Step 1.Step 3: Subtract the correction factor from the measured Total Sound Level. The resultant number is the Corrected Source Sound Level.
(g) Compliance determination will be based upon the Corrected Source Sound Level.(1) No violation shall be based upon any exceedance that is the result of numerical rounding. (2) Allowances shall be made for the accuracy of the meter, as per manufacturer's specifications.(3) A violation shall only be confirmed if the Corrected Source Sound Level exceeds both the permissible sound level limit (Table I) and the measured Ambient Sound Level. (Ord. 1612. Passed 4-13-15.)