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OSHA's noise standard treats two fundamentally different types of noise exposure under different measurement rules: continuous or steady-state noise (machinery hum, fans, conveyors) and impulse or impact noise (presses, nail guns, explosions). Understanding which type of noise your workers face—and how each is measured and regulated—is essential for accurate compliance determinations under 29 CFR 1910.95.
Soundtrace monitors both continuous and impulse noise sources, tracking dose accumulation across all exposure types in a single integrated platform.
Continuous noise is noise that persists at a relatively steady level throughout the work period. Examples include HVAC systems and fans, production conveyors and motors, air compressors, and grinding equipment. Continuous noise is measured using A-weighting (dBA) with slow response on an integrating SLM or personal dosimeter. The resulting TWA is compared against the 85 dBA action level and 90 dBA PEL.
Often steady-state; workers may be exposed across entire shifts without awareness due to habituation.
Consistent noise levels well-suited to TWA measurement with integrating SLM or dosimeter.
Often high-level continuous noise (85–100 dBA) that can dominate TWA for workers in proximity.
Continuous operation produces high steady-state levels for the operator.
Impulse noise consists of brief high-intensity peaks, each typically lasting less than 1 second. Both impulse and impact noise produce extremely high instantaneous sound pressure levels that can cause immediate acoustic trauma to the cochlea.
Gunshots, nail guns, explosive charges, air hammers, drop hammers. Each event is a discrete high-energy pulse with a rapid pressure rise and short duration.
Punch presses, stamping presses, rivet guns, forging hammers. Repetitive but each individual strike contributes a discrete high-level pulse to the accumulated dose.
Personal dosimeters using slow-response averaging may significantly undercount the actual acoustic energy delivered by impulse and impact noise events. For workplaces with significant impulse noise content, supplement dosimetry with peak measurements using a fast-response or peak-hold SLM.
| Exposure Type | OSHA Standard | Measurement Method | Key Limit |
|---|---|---|---|
| Continuous / steady-state | 1910.95(b)(1) TWA standard | Dosimeter or integrating SLM with slow response, A-weighting | 85 dBA action level; 90 dBA PEL TWA |
| Impulse / impact | 1910.95(b)(2) | Peak-hold SLM with fast or peak response | 140 dB peak sound pressure level (unweighted) |
OSHA applies two separate limits: a TWA limit for continuous noise (90 dBA for 8 hours) and a peak limit for impulse noise (140 dB peak SPL). Both limits must be evaluated independently for workplaces with both types of noise.
Instrument: Personal dosimeter or integrating SLM
Weighting: A-weighting (dBA)
Response: Slow
Threshold: 80 dBA (OSHA dosimeter setting)
Output: TWA in dBA, dose percentage
Use for: HCP enrollment decisions, PEL compliance
Instrument: Sound level meter with peak-hold function
Weighting: Unweighted (linear or Z-weighting)
Response: Fast or Peak
Output: Peak sound pressure level in dB SPL
Compare to: 140 dB peak limit per 1910.95(b)(2)
Also: Include impulse contributions in TWA dosimetry for full dose accounting
Many industrial workplaces have both continuous and impulse noise sources in the same area. Both exposure types must be evaluated independently against their respective limits, and the continuous component should still be measured via dosimetry for TWA compliance.
Soundtrace captures dose accumulation from all noise types and flags peak exceedances—giving you a complete picture of every worker’s exposure profile.
Book a DemoGet a quote for your facility →Under 1910.95(b)(2), impulse or impact noise is characterized by rapid pressure rises and brief durations. OSHA limits exposure to impulse or impact noise to a peak sound pressure level of 140 dB (unweighted) for any single event. This limit is measured separately from the TWA standard using a peak-hold sound level meter.
Standard personal dosimeters using slow-response averaging may significantly undercount the acoustic energy from impulse noise events. For workplaces with significant impulse or impact noise, supplement personal dosimetry with separate peak-hold measurements using a sound level meter with fast or peak response settings.
Yes. Both limits apply independently. Workers may be below the 90 dBA TWA continuous noise limit but still exceed the 140 dB peak impulse limit if exposed to high-intensity impact events. Both must be evaluated separately. Impulse noise contributions should also be included in full-shift dosimetry calculations.