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OSHA's noise standard establishes two exposure thresholds: the action level at 85 dBA TWA and the permissible exposure limit (PEL) at 90 dBA TWA. The 5 dB difference between them is not a gray zone—each threshold triggers a distinct and separate set of employer obligations. Understanding exactly what each level requires is the foundation of a compliant hearing conservation program.
Soundtrace automatically classifies workers against both thresholds and triggers the appropriate HCP actions based on real-time noise monitoring and dosimetry data.
The action level under 29 CFR 1910.95(b)(1) is a time-weighted average noise exposure of 85 dBA over an 8-hour shift. When a worker's measured or anticipated TWA equals or exceeds this level, the employer must:
Monitor noise exposure to quantify whether workers meet or exceed the action level. Repeat monitoring when conditions change.
Baseline audiogram within 6 months of first exposure; annual audiograms thereafter for as long as exposure continues.
Make hearing protection devices available at no cost. Employees at or above the action level must have access to HPDs even if not required to wear them.
Annual training on the effects of noise, HPD use and care, and the purpose of audiometric testing. Required every 12 months.
Retain noise monitoring records for 2 years; audiometric records for duration of employment. Make records available to employees upon request.
Inform workers of their monitoring results. Workers have the right to observe monitoring procedures.
Reaching the action level does not require engineering controls—it requires protection, monitoring, and a hearing conservation program. The distinction between action level and PEL is the difference between preventing exposure and actively controlling it.
The PEL is the maximum permissible noise dose for an 8-hour shift. When a worker's TWA equals or exceeds 90 dBA, all action level requirements continue to apply, and the employer must additionally implement engineering and administrative controls.
Implement feasible engineering controls to reduce noise at the source: machine enclosures, vibration isolation, damping materials, substitution of quieter equipment. Must be implemented even if hearing protection alone could theoretically protect the worker.
If engineering controls are not feasible or do not reduce exposure to the PEL, administrative controls must be implemented: limiting time in high-noise areas, rotating workers, restricting access. HPD is the last line, not the first.
Under 1910.95(b)(1), hearing protection devices cannot be used as a substitute for engineering or administrative controls when the PEL is exceeded and feasible controls exist. OSHA's hierarchy requires that employers first attempt to reduce exposure through controls. Relying solely on earplugs when engineering controls are feasible is a citable violation.
| Obligation | Action Level (85 dBA) | PEL (90 dBA) |
|---|---|---|
| Noise monitoring | Required | Required |
| Worker notification | Required | Required |
| Audiometric testing | Required | Required |
| HPD provision | Required (available at no cost) | Required (mandatory use if controls don't reach 90) |
| Annual training | Required | Required |
| Recordkeeping | Required | Required |
| Engineering controls | Not required | Required (if feasible) |
| Administrative controls | Not required | Required (if engineering not feasible) |
OSHA uses a 5 dB exchange rate, meaning that for every 5 dB increase in noise level, the permissible exposure time is cut in half.
A worker who spends 4 hours at 95 dBA and 2 hours at 100 dBA on the same shift has accumulated a noise dose equivalent to 8 hours at the PEL—the full daily limit—before the shift ends.
Soundtrace tracks noise exposure against the action level and PEL in real time, triggering audiometric enrollment, HPD requirements, and engineering control flags automatically.
Book a DemoGet a quote for your facility →The action level is 85 dBA TWA and triggers the full hearing conservation program: noise monitoring, audiometric testing, HPD provision, training, and recordkeeping. The PEL is 90 dBA TWA and triggers all HCP requirements plus the additional obligation to implement feasible engineering and administrative controls to actually reduce noise exposure. HPDs cannot substitute for controls when the PEL is exceeded and feasible controls exist.
No. Reaching the 85 dBA action level requires monitoring, audiometric testing, HPD provision, training, and recordkeeping—but does not mandate engineering controls. Engineering controls are only required under 1910.95(b)(1) when exposure exceeds the 90 dBA PEL and feasible controls are available.
OSHA uses a 5 dB exchange rate, meaning that for every 5 dB increase in noise level, the maximum permissible exposure time is cut in half. At 90 dBA, the maximum is 8 hours. At 95 dBA, 4 hours; at 100 dBA, 2 hours; at 115 dBA, 15 minutes. Workers exposed to multiple noise levels accumulate a combined dose evaluated against the full-shift limit.
No. Under 1910.95(b)(1), when the PEL is exceeded and feasible engineering or administrative controls exist, those controls must be implemented. Hearing protection can supplement controls for residual exposure, but cannot replace them when controls are technically and economically feasible. This is a commonly cited OSHA violation.