Noise Exposure Calculator
Enter a decibel level to calculate the maximum safe exposure time based on NIOSH criteria. The standard uses 85 dB as the reference (8 hours safe exposure) with a 3 dB exchange rate — every 3 dB increase doubles the risk and halves the allowable time.
Maximum safe exposure at
85 dB
8 hours
Moderate risk
NIOSH Formula
T = 8 × 2((85 − L) / 3) hours Where T = maximum exposure time, L = noise level in dB
Noise Exposure Reference Table
Common noise levels with their maximum safe exposure times based on the NIOSH 85 dB / 3 dB exchange rate standard.
| dB Level | Max Exposure | Examples | Risk Level |
|---|---|---|---|
| 70 dB | Unlimited | Conversation | Safe |
| 75 dB | Unlimited | Busy office | Safe |
| 80 dB | 25 hours | Alarm clock | Low risk |
| 85 dB | 8 hours | Heavy traffic | Moderate |
| 88 dB | 4 hours | Lawn mower | Moderate |
| 91 dB | 2 hours | Power tools | High |
| 94 dB | 1 hour | Motorcycle | High |
| 97 dB | 30 minutes | Nightclub | Very high |
| 100 dB | 15 minutes | Chainsaw | Very high |
| 103 dB | 7.5 minutes | Concert front row | Extreme |
| 106 dB | ~4 minutes | Jet takeoff (300m) | Extreme |
| 110 dB | ~2 minutes | Rock concert peak | Extreme |
| 115 dB | ~30 seconds | Siren at 1m | Immediate danger |
| 120+ dB | Immediate | Gunshot, jet engine | Pain threshold |
Understanding Noise Exposure Limits
Noise-induced hearing loss (NIHL) is one of the most common occupational health concerns worldwide. It's entirely preventable when you understand exposure limits and take appropriate precautions. This calculator uses the NIOSH recommended exposure limit (REL), which is considered more protective than the OSHA permissible exposure limit (PEL).
The key concept is the exchange rate — the number of decibels that doubles (or halves) the allowable exposure time. NIOSH uses a 3 dB exchange rate based on the equal-energy hypothesis: 3 dB represents a doubling of sound energy. OSHA uses a 5 dB exchange rate, which is less conservative and allows longer exposures at higher levels.
For most everyday scenarios, remember: 85 dB for 8 hours is your daily budget. If the level doubles to 88 dB, your time budget is cut in half to 4 hours. At a loud concert (100 dB), you have only about 15 minutes before risking permanent damage.
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Noise Exposure Calculator FAQ
What is the NIOSH noise exposure standard?
NIOSH (National Institute for Occupational Safety and Health) recommends a maximum exposure of 85 dB for 8 hours using a 3 dB exchange rate. This means every 3 dB increase halves the safe exposure time. At 88 dB you have 4 hours, at 91 dB just 2 hours, and so on.
What's the difference between NIOSH and OSHA noise standards?
NIOSH uses a 3 dB exchange rate (85 dB for 8 hours), while OSHA uses a 5 dB exchange rate (90 dB for 8 hours). NIOSH is more protective and scientifically conservative. OSHA's standard is a legal minimum for workplaces, but NIOSH recommendations better reflect actual hearing damage risk.
What is the 3 dB exchange rate?
The 3 dB exchange rate means that every 3 dB increase in noise level doubles the sound energy and halves the safe exposure time. Conversely, every 3 dB decrease doubles the allowable exposure. This is based on the equal-energy principle used in most international standards.
What is Time-Weighted Average (TWA)?
TWA is the average noise exposure normalized to an 8-hour workday. It accounts for varying noise levels throughout the day. If you spend 2 hours at 91 dB and 6 hours at 80 dB, your TWA is calculated by summing the dose fractions from each exposure period.
When should I wear hearing protection?
Wear hearing protection whenever noise exceeds 85 dB for extended periods. For concerts (100-110 dB), power tools (90-100 dB), or motorsports (95-110 dB), always use protection. Earplugs typically reduce noise by 15-30 dB depending on the type and fit.
Can short bursts of loud noise damage hearing?
Yes. Impulse noise like gunshots (140-170 dB) or explosions can cause immediate, permanent hearing damage in a single exposure. Even brief exposure to sounds above 120 dB (pain threshold) can harm the delicate hair cells in your inner ear.