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B. Measurements must be made using the A- weighting and fast response characteristics of the sound <br />measuring device as specified in American National Standards Institute S 1.4 -1983. <br />C. Measurements must not be made in sustained winds or in precipitation which results in a difference of <br />less than 10 decibels between the background noise level and the noise source being measured. <br />D. Measurements must be made using a microphone which is protected from ambient conditions which <br />would prevent an accurate measurement. <br />Subp. 5. Data documentation <br />A summary sheet for all sound level measurements shall be completed and signed by the person making the <br />measurements. At a minimum, the summary sheet shall include: <br />A. date <br />B. time <br />C. location <br />D. noise source <br />E. wind speed and direction <br />F. temperature <br />G. humidity <br />H. make, model, and serial number of measuring equipment <br />I. field calibration results <br />J. monitored levels <br />K. site sketch indicating noise source, measurement location, directions, distances, and obstructions <br />7030.0070 Sound attenuation measurement methodology <br />Subpart 1. Purpose <br />Sound level measurements made for assessing sound attenuation as specified in part 7030.0050, subpart 3, <br />item B, C, or D, shall be made according to the requirements of this part. <br />Subp. 2. Equipment <br />The equipment shall meet the requirements specified in part 7030.0060, subpart 2. <br />Subp. 3. Calibration <br />The equipment must meet the calibration requirements specified in part 7030.0060, subpart 3. <br />Subp. 4. Measurement procedure <br />The measurement procedure described in 25 FHWA- DP- 45 -1R, section 8 must be used for determination of <br />the sound attenuation. <br />Subp. 5. Equivalent methods <br />Methods equivalent to those described in subpart 4 may be used provided they are approved by the <br />commissioner of the MPCA. The commissioner shall approve an alternative method if the commissioner finds <br />that the method will produce representative data and results which are as reliable as the methods specified in <br />subpart 4. <br />7030.0080 Variance <br />If, upon written application of the responsible person, the agency finds that by reason of exceptional <br />circumstances strict conformity with any provisions of any noise rule would cause undue hardship, would be <br />unreasonable, impractical, or not feasible under the circumstances, the agency may permit a variance upon the <br />conditions and within the time limitations as it may prescribe for the prevention, control, or abatement of noise <br />pollution in harmony with the intent of the state and any applicable federal laws. <br />A Guide to Noise Control in <br />Minnesota • October 2008 Minnesota Pollution Control Agency <br />19 <br />