---
kind: "section"
citation: "49 C.F.R. § 325.9"
title: "49"
number: "325.9"
heading: "Measurement tolerances."
url: "https://uscodex.org/cfr/49/325.9"
---

# §325.9. Measurement tolerances.

- (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.

## Notes

### Authority

Authority: 42 U.S.C. 4917; 49 U.S.C. 301; and 49 CFR 1.87.

### Source

Source: 40 FR 42437, Sept. 12, 1975, unless otherwise noted.