Historical textIn force on Oct. 1, 2006Source: annual CFR editions 1998–2016

§ 325.79 Application of correction factors.

Wording in the annual edition revised as of Oct. 1, 1998, superseded January 1, 2017.

govinfo, 2006 edition ↗

Compare with

Before Jan. 1, 2017 the record is one snapshot per annual CFR edition, revised as of October 1. This is the 2006 edition's wording. An amendment that took effect between Oct. 1, 2006 and Oct. 1, 2006 would not appear until the next edition, so check the citations below and the Federal Register for exact effective dates.

49 CFR § 325.79 — Application of correction factors.. Text in force on October 1, 2006. This wording effective October 1, 1998 to January 1, 2017. Source: govinfo, 2006 edition, https://www.govinfo.gov/app/details/CFR-2006-title49-vol5/CFR-2006-title49-vol5-sec325-79. Retrieved from FMCSR.com, https://fmcsr.com/reg/325.79?asof=2006-10-01, on October 26, 2026. Unofficial compilation; verify against the official source.

(a) If two correction factors apply to a measurement they are applied cumulatively.

(b) The following examples illustrate the application of correction factors to sound level measurement readings:

(1) Example 1—Highway operations. Assume that a motor vehicle generates a maximum observed sound level reading of 86 dB(A) during a measurement in accordance with the rules in subpart D of this part. Assume also that the distance between the microphone location point and the microphone target point is 60 feet (18.3 m) and that the measurement area of the test site is acoustically “hard.” The corrected sound level generated by the motor vehicle would be 85 dB(A), calculated as follows:

86 dB(A) Uncorrected reading
+ 1 dB(A) Distance correction factor
−2 dB(A) Ground surface correction factor
_____
85 dB(A) Corrected reading

(2) Example 2—Stationary test. Assume that a motor vehicle generates maximum sound level readings which average 88 dB(A) during a measurement in accordance with the rules in subpart E of this part. Assume also that the distance between the microphone location point and the microphone target point is 35 feet (10.7 m), and that the measurement area of the test site is acoustically “soft.” The corrected sound level generated by the motor vehicle would be 87 dB(A), calculated as follows:

88 dB(A) Uncorrected average of readings
−3 dB(A) Distance correction factor
+ 2 dB(A) Ground surface correction factor
_____
87 dB(A) Corrected reading

Amendment history

3 distinct wordings on file since Oct. 1, 1996

Jan. 1, 2017 → presenteCFR, day-precisediff vs. previous
Oct. 1, 1998 → Jan. 1, 2017annual editions 1998–2016diff vs. previousviewing
Oct. 1, 1996 → Oct. 1, 1998annual edition 1996

A new entry appears whenever the regulatory words change between government snapshots. Day-precise from the eCFR (2017 onward); before that, one snapshot per annual CFR edition (revised as of October 1). Bracketed citations are the Federal Register history printed with the section.