Hearing safety · noise limits
Noise exposure allowed time.
Enter a sound level in dBA and see the daily exposure time NIOSH recommends (85 dBA, halve every 3 dB) next to what OSHA permits (90 dBA, halve every 5 dB).
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Enter a sound level in dBA.
NIOSH and OSHA limits compared
Two different rules apply, and they are not interchangeable. NIOSH (a research agency) recommends an exposure limit of 85 dBA as an 8-hour average with a 3 dB exchange rate: every 3 dB louder halves the allowed time. OSHA (the US regulator) sets a permissible exposure limit of 90 dBA over 8 hours with a 5 dB exchange rate, and requires a hearing conservation program from an 8-hour average of 85 dBA (the action level). The formulas are NIOSH: T (minutes) = 480 / 2^((L - 85) / 3) and OSHA: T (hours) = 8 / 2^((L - 90) / 5).
Worked example. At 94 dBA, NIOSH allows 60 minutes per day and OSHA allows 4.6 hours. At 100 dBA, NIOSH allows 15 minutes and OSHA 2 hours. At 88 dBA NIOSH allows 4 hours, while OSHA does not limit it at all because it is under 90 dBA.
| Level | NIOSH allowed | OSHA allowed |
|---|---|---|
| 82 dBA | 16 hours | 24.3 hours |
| 85 dBA | 8 hours | 16 hours |
| 88 dBA | 4 hours | 10.6 hours |
| 91 dBA | 2 hours | 7 hours |
| 94 dBA | 60 minutes | 4.6 hours |
| 97 dBA | 30 minutes | 3 hours |
| 100 dBA | 15 minutes | 2 hours |
| 103 dBA | 7.5 minutes | 79.2 minutes |
| 106 dBA | 3.8 minutes | 52.2 minutes |
| 109 dBA | 1.9 minutes | 34.5 minutes |
| 112 dBA | 56 seconds | 22.7 minutes |
| 115 dBA | 28 seconds | 15 minutes |
OSHA's own Table G-16 lists rounded whole values (for example 6 hours at 92 dBA and 3 hours at 97 dBA); the table above uses the formula, which gives 6.1 and 3.0 hours. Above 115 dBA OSHA's table ends at 15 minutes or less. Several levels at different times in one day need the dose calculation: use the noise dose and TWA calculator.
Both limits assume A-weighted, slow-response measurements. NIOSH says that "everyone differs in their susceptibility to noise", so staying at the limit is not a guarantee of no damage.
Frequently asked questions
How loud is too loud for 8 hours?
NIOSH recommends keeping an 8-hour average under 85 dBA. OSHA's legal limit is 90 dBA over 8 hours, with a hearing conservation program required from 85 dBA.
What is the 3 dB exchange rate?
It means the allowed time is cut in half for every 3 dB increase in level. OSHA uses a 5 dB exchange rate instead, which allows longer times at the same level.
Why do NIOSH and OSHA give different times?
NIOSH is a recommendation based on the research on hearing loss risk. OSHA is a regulation with an older, more permissive limit and exchange rate. Both are shown so you can see the gap.
Does this apply to music and headphones?
The limits are workplace limits. They are a reasonable yardstick for recreational noise, but the level must be measured in dBA, not read off a volume slider.
Sources
Checked
- NIOSH 98-126: Criteria for a Recommended Standard, Occupational Noise Exposure, Revised Criteria 1998
- CDC NIOSH: Noise-Induced Hearing Loss
- CDC NIOSH: Understand Noise Exposure
- OSHA 29 CFR 1910.95: Occupational noise exposure
- OSHA 1910.95 Appendix A: Noise exposure computation
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Hearing safety guidance, not medical or occupational-health advice. These are published limits and rules of thumb applied as arithmetic, not a noise survey. Measure real levels with a sound level meter or dosimeter, follow the rules that apply to your workplace, and see an audiologist if you have ringing, muffled hearing or hearing loss.