49 CFR §325.9
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
- (a)Measurement tolerances will be allowed to take into account the effects of the following factors:
- (1)The consensus standard practice of reporting filed sound level measurements to the nearest whole decibel.
- (2)Variations resulting from commercial instrument tolerances.
- (3)Variations resulting from the topography of the noise measurement site.
- (4)Variations resulting from atmospheric conditions such as wind, ambient temperature, and atmospheric pressure.
- (5)Variations resulting from reflected sound from small objects allowed within the test site.
- (6)The interpretation of the effects of the above cited factors by enforcement personnel.
- (b)Measurement tolerances shall not exceed 2 decibels for a given measurement.