OSHA Noise Level Requirements: Action Level, PEL, and What Each One Triggers

OSHA’s noise requirements come in layers — and most summaries either oversimplify them to a single number or bury the key distinctions in regulatory language. This guide gives you the complete picture: what the limits are, what they trigger, how exposure is measured, and what the difference between the action level and the PEL actually means for your program.

Soundtrace helps employers understand exactly where their workforce falls relative to OSHA’s noise thresholds — with integrated noise monitoring and audiometric testing that responds appropriately at both the 85 dBA action level and the 90 dBA PEL.

The Two Thresholds: Action Level and PEL

OSHA’s noise regulation establishes two critical thresholds, not one. Confusion between them is the most common misunderstanding in occupational noise compliance:

The Action Level (AL): 85 dBA TWA
The action level triggers the requirement for a hearing conservation program. When any employee’s noise exposure equals or exceeds 85 dBA as an 8-hour time-weighted average, the employer must: conduct noise monitoring, provide audiometric testing, make hearing protection available, train employees annually, and maintain records. The action level does not require engineering controls — it requires a hearing conservation program.

The Permissible Exposure Limit (PEL): 90 dBA TWA
The PEL is the upper bound of permissible noise exposure. When any employee’s noise exposure equals or exceeds 90 dBA TWA, the employer must: implement feasible engineering and administrative controls to reduce exposure, use hearing protection as a supplement if controls alone can’t achieve the PEL, and ensure that hearing protection adequately reduces exposure to or below the PEL. The PEL triggers the engineering control obligation.

These are separate obligations that apply at different exposure levels. An employee exposed at 88 dBA TWA is above the action level (hearing conservation program required) but below the PEL (engineering controls not yet mandated). An employee at 95 dBA TWA is above both thresholds and requires both the full HCP and feasible engineering controls.

▶ Bottom line: Action level (85 dBA) = hearing conservation program. PEL (90 dBA) = engineering controls. These are different thresholds with different compliance obligations and must not be conflated.

What Each Threshold Triggers: A Complete Reference

▶ Bottom line: The action level is the compliance-intensive threshold — it triggers nine distinct regulatory requirements. The PEL adds the engineering control obligation and changes hearing protection from voluntary to mandatory.

How OSHA Noise Exposure Is Measured

OSHA specifies that noise monitoring must be capable of measuring all continuous, intermittent, and impulsive noise in the 80–130 dBA range and must integrate exposures over the measurement period to produce a time-weighted average. Two methods are recognized:

Personal noise dosimetry: A dosimeter worn on the worker’s shoulder with a microphone near the ear continuously measures and integrates noise levels throughout the shift. The result is the total dose expressed as a percentage of the permissible daily exposure, and the equivalent 8-hour TWA. This is the standard method for variable or mobile work environments.

Sound level measurements with integration: Area sound level measurements using integrating sound level meters can be appropriate for workers who stay in one location with relatively constant noise levels. However, area measurements cannot capture the full dose of a worker who moves between areas or operates different equipment across the shift.

Instruments must meet ANSI S1.4-1971 (R1976) Type 2 accuracy requirements at minimum. The threshold level for dose integration must be set at 80 dBA (to capture all noise contributing to the action level assessment) and the exchange rate at 5 dB (OSHA standard).

▶ Bottom line: For workers with variable noise exposures or who move between areas, personal dosimetry is the only way to accurately measure the total dose. Area measurements systematically underestimate or overestimate individual exposure depending on the worker’s movement patterns.

The Exchange Rate: What It Means for Permissible Durations

The exchange rate — also called the time-intensity tradeoff — determines how much additional noise level requires halving the permissible exposure time. OSHA uses a 5 dB exchange rate. Every 5 dB increase in noise level halves the allowable exposure duration:

The formula for calculating TWA from dose: TWA = 16.61 log(D/100) + 90, where D is the percent dose measured by the dosimeter. Workers who accumulate 100% dose have reached the PEL; workers who accumulate dose corresponding to the action level equivalent (50% dose using the PEL criterion level) have crossed the action level.

▶ Bottom line: At noise levels above 100 dBA, permissible exposure times under OSHA’s standard are measured in minutes per shift. Workers in brief but very high noise exposure situations — near pneumatic hammers, metal shears, or jet engines — may cross the PEL in minutes regardless of the full-shift average.

Impulsive and Impact Noise: A Separate Standard

OSHA 1910.95(b)(2) specifies that exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level. This is a separate limit from the TWA-based PEL and applies regardless of exposure duration — a single impulse above 140 dB peak is a violation regardless of whether the 8-hour TWA is below the PEL.

Impulsive noise sources in industrial settings include: metal stamping presses, pneumatic impact wrenches, explosive-actuated fasteners, gunfire, and certain industrial process sounds with rapid pressure transients. Standard dosimeters using slow or fast response settings may significantly underestimate peak impulsive noise levels — measurements of peak impulsive noise require specialized equipment or dosimeters with impulse peak measurement capability.

▶ Bottom line: The 140 dB peak limit for impulsive noise is a separate, absolute ceiling — not averaged, not time-weighted. One event above 140 dB peak is a violation, regardless of the rest of the shift profile.

Construction vs. General Industry Noise Standards

Construction workers are covered by 29 CFR 1926.52, which uses the same Table D-2 permissible exposure levels as the general industry Table G-16 — 90 dBA PEL for 8-hour TWA, 5 dB exchange rate. The construction standard also requires feasible engineering and administrative controls when exposures exceed the PEL, and requires hearing protection under 1926.101 when controls are insufficient.

The critical difference: the construction standard does not include the comprehensive hearing conservation program requirements of 1910.95. There is no explicit requirement for audiometric testing, training to specific content standards, or the formal recordkeeping framework of 1910.95(m). This regulatory gap has been recognized as inadequate given the high noise levels in construction operations.

Where NIOSH Differs from OSHA: The REL

NIOSH recommends a more protective noise standard than OSHA based on current understanding of noise-induced hearing damage:

• NIOSH REL: 85 dBA TWA using a 3 dB exchange rate (equal energy rule)
• OSHA PEL: 90 dBA TWA using a 5 dB exchange rate

The 3 dB exchange rate, based on the physics of sound energy accumulation, means that for every 3 dB increase in level, the permissible duration is halved. At 95 dBA, NIOSH allows approximately 47 minutes; OSHA allows 4 hours. At 100 dBA, NIOSH allows approximately 15 minutes; OSHA allows 2 hours.

NIOSH’s REL is not an enforceable OSHA standard, but it represents the current scientific consensus on what level of noise exposure is safe for lifetime occupational health. Programs that evaluate exposure against NIOSH criteria provide a more health-protective assessment and may identify workers at risk who are below the OSHA action level but above NIOSH’s recommended limits.