Sound level means the quantity in decibles measured by a sound level meter satisfying the requirements of American National Standards Specification for Sound Level Meters S1.41971. This publication is available from the American National Standards Institute, Inc., 1430 Broadway, New York, New York 10018. Sound level is the frequency-weighted sound pressure level obtained with the standardized dynamic characteristic fast or slow and weighting A, B, or C; unless indicated otherwise, the A-weighting is understood.
40 CFR § 202.10
As used in this part, all terms not defined herein shall have the meaning given them in the Act: