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OSHA issues letters of interpretation to answer specific compliance questions from employers, industry groups, and the public. These letters clarify how OSHA interprets a regulatory provision, and OSHA is expected to enforce consistently with its own published interpretations. For the hearing conservation standard (29 CFR 1910.95), dozens of interpretation letters have been issued since the standard’s 1983 promulgation — clarifying everything from who qualifies as a Professional Supervisor to whether temporary workers must be included in audiometric testing. These are the 10 most practically important rulings for employers managing a hearing conservation program in 2026.
Soundtrace’s compliance model was independently assessed in January 2026 by Scott Ketcham, CSP (former Director of OSHA’s Directorate of Enforcement Programs), and is designed to satisfy the obligations clarified by the letters of interpretation discussed here.
OSHA compliance officers use letters of interpretation to guide enforcement decisions. An employer whose program aligns with relevant LOI guidance has a stronger position in a citation dispute. An employer who is unaware that OSHA has already answered a disputed question — and answered it unfavorably — has no defense based on good-faith misunderstanding. LOIs are not regulations, but they are OSHA’s stated enforcement position, and they are legally significant in any contested citation proceeding.
OSHA has consistently interpreted “supervised by” in 1910.95(g)(3) to mean that the Professional Supervisor reviews and accepts clinical responsibility for results — not that they must be physically present at each test. A microprocessor audiometer that presents stimuli, records responses, and flags results for PS review satisfies the supervision requirement without real-time clinician presence. This is the cornerstone LOI for Soundtrace’s automated audiometry model and for any boothless or remote audiometric testing program.
OSHA’s 2019 response to Silver Bay Seafoods addressed whether a salmon processing company’s seasonal workers — employed for 2–4 months — were exempt from audiometric testing requirements. OSHA confirmed they are not. All HCP elements apply from day one of qualifying noise exposure. The 6-month audiometric testing window means that very short assignments effectively run out before the test is due, but the obligation exists and the employer must track it. OSHA acknowledged the administrative difficulty but did not create an exemption.
OSHA’s language in 1910.95(g)(3) requires that audiometric tests be administered by a “licensed or certified audiometric technician.” OSHA has interpreted “certified” to include CAOHC certification but not to require it exclusively. An employer who documents its own technician training and testing program, demonstrates competence through that program, and has PS oversight satisfies the standard. This interpretation supports alternative training models for operators of automated audiometric systems.
OSHA has clarified that the two audiometric thresholds — the 10 dB STS determination and the 25 dB above audiometric zero recordability criterion — operate independently. Age correction is a 1910.95 tool only. When determining whether a 300 Log entry is required, the worker’s actual unadjusted threshold is measured against audiometric zero. An employer who applies age correction to eliminate a recordable 300 Log entry has violated 1904.10, even if the age-corrected STS does not trigger the follow-up obligations under 1910.95(g)(8).
OSHA clarified that the retest provision in 1910.95(g)(7)(ii) is designed to eliminate false-positive STSs that result from temporary threshold shift, equipment variation, or test conditions. If the retest result is better than the threshold required for an STS, the employer may use the retest result for purposes of determining whether an STS occurred. This is not a credit toward a future STS — it is a full substitution of the annual audiogram for purposes of the STS determination. Both audiograms must be retained in the worker’s record.
OSHA has confirmed that the revised baseline provision in 1910.95(g)(9) vests authority in the Professional Supervisor. An employer cannot instruct a testing vendor to revise a worker’s baseline simply because the employer prefers the new audiogram as a reference point. The PS must independently determine that the STS is persistent or that significant improvement has occurred. This interpretation makes it essential that the PS role is occupied by a genuinely independent and qualified clinician, not merely a name on a supervision form.
OSHA clarified the distinction between availability and mandatory use early in the 1983 rulemaking interpretive history. At the action level, HPD must be provided at no cost and employees must be trained on its use — but use is not technically mandated unless the employee elects it or has an STS. At the PEL (90 dBA), use is mandatory. After an STS, HPD use becomes mandatory for the affected worker even if their exposure is at or just above the action level.
OSHA’s multi-employer worksite policy and specific 1910.95 interpretations confirm that the host employer cannot simply exclude contract or vendor workers from its noise hazard disclosures on the grounds that they are not direct employees. The host employer controls the noise environment and must ensure it does not expose visiting workers to noise without at minimum informing them of the hazard. The audiometric program responsibility, however, follows the employment relationship.
OSHA clarified that there is no exception for mobile testing from the Appendix D acoustic environment requirements. A mobile audiometric testing van whose interior exceeds the Appendix D octave-band noise limits is not a compliant testing environment, regardless of the convenience it offers. Van operators must periodically verify background noise levels and document that testing occurs within compliant acoustic conditions. This is the same obligation that fixed-room testing programs carry.
This LOI is relevant to employers with mixed federal and private operations, and to Soundtrace clients who may operate in state-plan states like California, Oregon, Washington, or Virginia. A private employer in Oregon operating under OSHA’s state plan (OAR Ch. 437) may have additional requirements beyond federal 1910.95, including CAOHC certification for audiometric technicians. A federal agency employee in Oregon working at a federal facility is not subject to Oregon OSHA’s plan. Understanding the jurisdictional boundary is essential for multi-employer, multi-site operations in state-plan states.
Soundtrace’s hearing conservation program model is designed to satisfy the compliance standards established in OSHA’s own letters of interpretation — including the microprocessor audiometer supervision model, the demonstrated competence standard for operators, and the Invisible Booth™ acoustic validation methodology.
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