49 C.F.R. § D to Part 227
This appendix is mandatory.
A. Rooms used for audiometric testing shall not have background sound pressure levels exceeding those in Table D-1 when measured by equipment conforming at least to the Type 2 requirements of ANSI S1.4-1983 (Reaffirmed 2001) and to the Class 2 requirements of ANSI S1.11-2004, "Specification for Octave-Band and Fractional-Octave-Band Analog and Digital Filters."
B. The Director of the Federal Register approves the incorporation by reference of ANSI S1.4-1983 (Reaffirmed 2001) and S.1.11-2004 in this section in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 . You may obtain a copy of the incorporated standard from the American National Standards Institute at 1819 L Street, NW., Washington, DC 20036 or http://www.ansi.org. You may inspect a copy of the incorporated standard at the Federal Railroad Administration, Docket Room, 1200 New Jersey Avenue, SE., Washington, DC 20590, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
Table D-1-Maximum Allowable Octave-Band Sound Pressure Levels for Audiometric Test Rooms
| Octave-band center frequency (Hz) | 500 | 1000 | 2000 | 4000 | 8000 |
| Sound pressure levels-supra-aural earphones | 40 | 40 | 47 | 57 | 62 |
| Sound pressure levels-insert earphones | 50 | 47 | 49 | 50 | 56 |
49 C.F.R. §D to Part 227