49 CFR §325.31
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
The rules in this subpart specify conditions and procedures for measurement of the sound level generated by a motor vehicle engaged in a highway operation for the purpose of ascertaining whether the motor vehicle conforms to the Standards for Highway Operations set forth in 40 CFR 202.20.