Understanding audiogram patterns is essential for EHS managers who review occupational audiometric surveillance results. This guide covers baseline revision: what it looks like on an audiogram, what it means clinically, what OSHA 1910.95 obligations it triggers, and the required employer response. Note that audiogram interpretation in the context of OSHA compliance always requires involvement of a licensed Professional Supervisor — a licensed audiologist, otolaryngologist, or other physician. The EHS manager's role is to understand the pattern well enough to act appropriately and ensure timely PS review.
Soundtrace provides audiometric testing supervised by a licensed audiologist who reviews all audiograms, identifies STSs, and makes clinical determinations — ensuring employer compliance with every 1910.95 audiometric obligation.
What Is Baseline Revision?
Baseline revision is the process of replacing the original OSHA baseline audiogram with a more recent audiogram for purposes of future STS calculations. OSHA 1910.95 permits two types: (1) mandatory revision when a subsequent audiogram shows significantly better thresholds (the better audiogram becomes the new baseline); and (2) discretionary revision when the Professional Supervisor determines the original baseline was invalid due to temporary threshold shift, equipment error, or other factors at the time of testing.
Clinical Significance
The baseline audiogram anchors all future STS calculations. A poor-quality original baseline — contaminated by TTS, recorded in a non-compliant test environment, or affected by calibration errors — produces an artificially elevated reference point that may suppress future STSs (because the shift is calculated from an already-elevated starting point) or create false positives. Baseline revision corrects these problems by substituting a valid reference audiogram. The Professional Supervisor's clinical judgment is central to baseline revision decisions.
All clinical interpretations of occupational audiograms — including determinations of audiogram pattern, work-relatedness, and STS confirmation — must be made by the Professional Supervisor (licensed audiologist, otolaryngologist, or other physician) under OSHA 1910.95(g)(3). EHS managers should understand these patterns to recognize when PS review is needed and to act on PS findings promptly, not to replace the PS role.
OSHA 1910.95 Implications
OSHA 1910.95 Appendix F and 1910.95(g)(7) address baseline revision. Key provisions: if a subsequent audiogram shows better thresholds than the original baseline, the improved audiogram must be used as the new baseline (mandatory upgrade). If the PS determines the original baseline was invalid, they may substitute a more valid audiogram as the new baseline. Baseline revision does not eliminate the STS analysis for the period between the original and revised baseline — the employer must document why the revision was made and what the clinical rationale was.
Required Employer Response
Baseline revisions are clinical decisions that require Professional Supervisor involvement and documentation. An EHS manager changing baseline records without PS review is creating compliance and litigation risk.
Every baseline revision must be documented with: the clinical rationale for revision, the audiograms being compared, the PS's conclusion, and the date of revision. This documentation is essential if the revision is questioned in a WC proceeding.
If an annual audiogram shows thresholds better than the original baseline (e.g., a new baseline at 15 dBHL at 4 kHz vs. the original 20 dBHL), the better audiogram becomes the new baseline. Future STSs are calculated from this improved reference. This rule exists to ensure STSs are calculated from the worker's best-documented hearing thresholds.
Audiologist-supervised audiometric testing with automatic STS detection
Soundtrace audiometric testing is supervised by a licensed audiologist who reviews every audiogram, identifies all STSs, and makes clinical determinations — ensuring your program meets every 1910.95 requirement.
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Baseline revision is the process of replacing the original OSHA baseline audiogram with a more recent audiogram for purposes of future STS calculations. OSHA 1910.95 permits two types: (1) mandatory revision when a subsequent audiogram shows significantly better thresholds (the better audiogram becomes the new baseline); and (2) discretionary revis
OSHA 1910.95 Appendix F and 1910.95(g)(7) address baseline revision. Key provisions: if a subsequent audiogram shows better thresholds than the original baseline, the improved audiogram must be used as the new baseline (mandatory upgrade). If the PS determines the original baseline was invalid, they. The Professional Supervisor must review all audiograms with significant findings to determine STS status and work-relatedness.
The Professional Supervisor — a licensed audiologist, otolaryngologist, or other physician — must review any audiogram with clinically significant findings. OSHA 1910.95(g)(3) requires PS involvement in all STS determinations and medical referral decisions. EHS managers should not attempt to interpret audiogram patterns independently.