OSHA 1910.95 Overview

29 CFR 1910.95 is the US federal standard for occupational noise exposure. It establishes permissible exposure limits and requires employers to implement hearing conservation programs when workers are exposed above specified thresholds. The standard references ANSI S1.4 for instrumentation and ANSI S1.4A for Lavg/TWA calculation.

Exposure Limits

Threshold	Level	Required action
Permissible Exposure Limit (PEL)	TWA 90 dBA	Engineering/admin controls required
Action Level	TWA 85 dBA	Hearing Conservation Program
Maximum continuous	115 dBA	No exposure without HPD
Peak	140 dB	Never exceeded

The 5 dB exchange rate means: 90 dBA for 8 hours = 95 dBA for 4 hours = 100 dBA for 2 hours = 105 dBA for 1 hour.

Hearing Conservation Program

When employee exposure equals or exceeds TWA 85 dBA (Action Level), employers must:

Monitor: Conduct noise monitoring with Type 2 instruments or personal dosimeters
Audiometric testing: Baseline and annual audiograms for exposed workers
Hearing protection: Provide HPDs (earplugs, earmuffs) and ensure proper use
Training: Annual training on noise hazards, HPD use, and audiometric testing
Recordkeeping: Maintain monitoring records, audiometric results, calibration records

Measurement Requirements

OSHA specifies:

Sound level meter: A-weighting, Slow response, Type 2 or better per ANSI S1.4
Noise dosimeter: conforming to ANSI S1.25, A-weighting, 5 dB exchange rate, 90 dBA criterion level
Calibration before each day's use
Monitoring must capture representative worst-case exposure

Hearing Protection Derating

OSHA uses the NRR (Noise Reduction Rating) printed on HPD packaging with a derating formula: effective protection = (NRR - 7) / 2 when using dBA measurements. For example, earplugs rated NRR 29 provide (29-7)/2 = 11 dB of effective protection. NIOSH recommends even more conservative derating (50% of NRR for earmuffs, 25% for earplugs). The noise dose calculator includes HPD effectiveness calculation with both methods.

OSHA vs NIOSH vs EU

NIOSH recommends stricter limits: 85 dBA PEL with 3 dB exchange rate. The EU Directive 2003/10/EC uses similar thresholds to NIOSH with action values at 80 and 85 dBA. OSHA's 5 dB exchange rate and 90 dBA PEL are less protective than international standards.

SonaVyx OSHA Tools

The noise dose calculator supports both OSHA and ISO/NIOSH standards with real-time dose accumulation, TWA display, and HPD derating. The SPL meter shows A-weighted levels with OSHA 85/90 dBA threshold lines. For environmental factors affecting field measurements, see the environmental section.