OSHA letters of interpretation are the compliance practitioner's primary tool for understanding how OSHA actually applies 29 CFR 1910.95 to real-world situations. When the regulatory text is ambiguous or silent on a specific compliance question, letters of interpretation fill the gap — and knowing which letters are relevant to hearing conservation programs is essential for EHS professionals building defensible programs. According to CDC/NIOSH, approximately 22 million U.S. workers face hazardous noise annually, and the program decisions that protect employers and workers are often guided by interpretation letters rather than the regulatory text alone.
What OSHA Letters of Interpretation Are
An OSHA letter of interpretation is an official written response from OSHA to a compliance question. They are issued by OSHA’s Office of General Industry and Agricultural Enforcement or relevant directorate in response to questions submitted by employers, industry associations, standards bodies, or individuals. They address specific situations: does this audiometer type comply with ANSI S3.6? Does this test environment meet ANSI S3.1-1999 MPANLs? Can a CAOHC-certified technician serve as Professional Supervisor?
Letters of interpretation are not regulations — they cannot create new obligations beyond what the standard itself requires — but they represent OSHA’s enforcement position. OSHA inspectors use them to guide citations; employers cite them in their defense. A letter of interpretation establishing that a specific practice is compliant provides a good-faith compliance defense if OSHA later contradicts that position.
OSHA occasionally withdraws or modifies letters of interpretation. A letter that was issued in 2005 may not reflect current OSHA enforcement policy if the agency has issued a subsequent letter modifying or superseding it. Always verify that a letter of interpretation you are relying on has not been withdrawn. OSHA’s interpretation letter database indicates withdrawn letters.
Key Hearing Conservation Interpretation Letters
| Letter Date | Topic | Key Holding |
|---|---|---|
| Oct 11, 2022 | ANSI S3.1-1999 MPANL compliance for microprocessor audiometers | ANSI S3.1-1999 (R2018) maximum permissible ambient noise levels satisfy OSHA Appendix D requirements for audiometric test environments |
| Various | Professional Supervisor qualifications | A licensed audiologist or physician may serve as Professional Supervisor; CAOHC certification alone does not satisfy the Professional Supervisor requirement |
| Various | Microprocessor audiometer compliance | Automated microprocessor audiometers meeting ANSI S3.6 satisfy OSHA’s audiometer standard requirements; Type 4 automated audiometers are specifically addressed |
| Various | STS calculation and age correction | Age correction using Appendix F tables is permissible but not required; employers may apply age correction to reduce apparent STS when the shift reflects age-related rather than noise-induced change |
The October 11, 2022 OSHA letter of interpretation confirms that ANSI S3.1-1999 (R2018) maximum permissible ambient noise levels satisfy Appendix D requirements for audiometric test environments. This letter directly supports Soundtrace’s program design, which uses ANSI S3.1-1999 (R2018) compliant test environments. Clients can reference this letter in any OSHA compliance inquiry about audiometric test environment standards.
Frequently Asked Questions
Programs Built to OSHA Interpretation Letter Standards
Soundtrace program design is informed by key OSHA letters of interpretation — including the Oct 11, 2022 letter on ANSI S3.1-1999 compliance — giving clients the documentation basis for defensible programs.
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