OSHA 29 CFR 1910.95 Appendix D — Audiometric Test Rooms — Appendix D to OSHA 1910.95 incorporates by reference the American National Standard Specification for Sound Level Meters (ANSI S3.1-1999, reaffirmed 2018), which establishes the Maximum Permissible Ambient Noise Levels (MPANLs) for audiometric test environments. This is the standard that governs where and under what conditions an OSHA-compliant audiogram can be conducted. This plain-language guide explains what Appendix D requires, what it means in practice for EHS managers, and how it connects to the broader OSHA 1910.95 hearing conservation program requirements. According to CDC/NIOSH, approximately 22 million U.S. workers are exposed to hazardous occupational noise annually.
Soundtrace delivers audiometric testing and noise monitoring that meets the technical requirements of all 1910.95 appendices — including ANSI S3.1 ambient noise validation per audiogram and ANSI S3.6 audiometer specifications.
What Are Maximum Permissible Ambient Noise Levels?
MPANLs are the maximum background noise levels at each audiometric test frequency that are acceptable in an audiometric test environment. If ambient noise in the test room exceeds these levels at any test frequency, tones at that frequency may be masked by background noise, causing the worker to appear to have worse hearing than they actually do. This produces an artificially elevated threshold that is not a valid audiometric measurement.
ANSI S3.1 MPANL Table (Key Frequencies)
| Test Frequency (Hz) | MPANL with Supra-Aural Earphones (dB SPL) |
|---|---|
| 500 | 40 |
| 1000 | 40 |
| 2000 | 47 |
| 3000 | 52 |
| 4000 | 57 |
| 6000 | 62 |
These are the octave-band levels at the test frequencies in the test environment. If the ambient noise in a break room at 500 Hz exceeds 40 dB SPL, audiometric testing at 500 Hz in that room produces invalid results.
Why This Matters for Employers
Many employers incorrectly assume audiometric testing can be conducted anywhere with a portable audiometer. The test environment must meet these specific frequency-by-frequency limits regardless of how quiet it sounds to the human ear. A room that feels quiet may still fail the 500 Hz octave band limit due to HVAC hum or distant equipment vibration.
Audiograms conducted in environments exceeding ANSI S3.1-1999 MPANLs are not valid for OSHA compliance purposes. They cannot be used for STS calculations, WC defense, or as evidence of HCP compliance during an OSHA inspection. The cost of a non-compliant test environment is measured in potentially invalidated years of audiometric records.
Documenting ANSI S3.1 Compliance
OSHA does not specify a documentation format, but best practice is to retain records of ambient noise measurements at the test frequencies for each test environment used. Soundtrace documents frequency-specific ambient noise conditions at the time of each individual audiogram, creating per-audiogram documentation of test environment compliance. See: ambient noise compliance and audiometric testing protocol.
Boothless audiometry and Appendix D
Boothless audiometry — testing without a traditional soundproof booth — must still meet ANSI S3.1-1999 MPANLs. The test environment must be verified at the test frequencies regardless of whether a booth is used. A calibrated quiet space that meets the frequency-specific limits qualifies; an unverified break room does not. See: boothless audiometry and OSHA compliance.
OSHA 1910.95 compliant audiometric testing — every appendix requirement met
Soundtrace delivers audiometric testing that meets ANSI S3.1 test environment requirements (Appendix D), uses ANSI S3.6 calibrated audiometers, and is supervised by a licensed audiologist — fully compliant with every 1910.95 appendix requirement.
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