Workplace noise monitoring is the first compliance step under OSHA 1910.95: it determines which employees must be enrolled in the hearing conservation program, what hearing protection is required, and what records must be maintained. Done correctly, it also creates the evidentiary foundation that defends against occupational hearing loss claims by documenting actual exposure levels during the relevant employment period.
Soundtrace captures frequency-specific ambient noise data linked to every individual audiogram — event-level documentation that goes beyond periodic area monitoring and provides stronger evidentiary support for both OSHA compliance and WC defense.
Noise monitoring records have two lives: compliance and legal. A monitoring record from years ago that documents TWA levels below the PEL is strong evidence that a worker’s hearing loss was not caused by that employer’s workplace. The employer who retains monitoring records well beyond the OSHA two-year minimum has built a defense that cannot be reconstructed after the fact.
Why Noise Monitoring Is Required
OSHA 1910.95(d) requires monitoring when information indicates that any employee’s exposure may equal or exceed the action level of 85 dBA. Re-monitoring is required whenever a change in production, process, equipment, or controls may have increased noise exposures.
OSHA Exposure Limits Explained
The action level of 85 dBA as an 8-hour TWA triggers HCP requirements. The PEL of 90 dBA as an 8-hour TWA triggers mandatory HPD use and engineering or administrative controls. NIOSH uses a stricter REL of 85 dBA with a 3 dB exchange rate.
Real-World Noise Levels Reference
| Source / Operation | Typical Range (dBA) | Action Level Risk |
|---|---|---|
| Normal conversation | 55–65 | None |
| Fork lift, warehouse | 75–85 | Borderline |
| Circular saw, power tools | 85–95 | Yes |
| Packaging machinery | 85–95 | Yes |
| Metal stamping press | 95–105 | Above PEL |
| Pneumatic tools (impact) | 95–115 | Above PEL |
| Shotblasting, abrasive blasting | 105–115 | Above PEL |
Sound Level Meters vs. Noise Dosimeters
Sound level meters measure instantaneous or short-term noise levels at a fixed location. For individual exposure assessments, a noise dosimeter worn by the worker throughout the shift is required. Both instruments must be calibrated before and after each use, with formal annual calibration. Calibration records must be retained.
How to Conduct a Workplace Noise Survey
A workplace noise survey begins with a facility walk-through to identify all significant noise sources. Area readings establish a noise map. Any area with consistent readings at or near 85 dBA should be flagged for personal dosimetry. Survey results must be shared with affected employees.
Understanding TWA and Noise Dose
| Level (dBA) | OSHA Permissible Duration | NIOSH Permissible Duration |
|---|---|---|
| 85 dBA | 16 hrs (below PEL) | 8 hrs (NIOSH REL) |
| 90 dBA | 8 hrs (PEL) | 2.5 hrs |
| 95 dBA | 4 hrs | 47 min |
| 100 dBA | 2 hrs | 15 min |
| 105 dBA | 1 hr | 5 min |
| 115 dBA | 15 min (OSHA ceiling) | <1 min |
Continuous vs. Impulse Noise
Continuous noise is captured well by standard dosimetry. Impulse noise (impacts, gunshots, air tools) requires specialized measurement. Workers exposed to impulse noise above 140 dB peak require specific controls regardless of TWA calculations.
Noise exposure data linked to every audiogram, not just periodic surveys
Soundtrace documents frequency-specific ambient noise levels at the time of each individual audiogram — creating event-level noise validation that goes beyond periodic area monitoring.
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