Noise Exposure Calculator

Noise exposure limits protect hearing. Two major standards exist: OSHA and NIOSH.

OSHA Permissible Exposure Limits (PEL): Uses a 5 dB exchange rate (doubling rate).

• 85 dB: 16 hours
• 90 dB: 8 hours (the reference level)
• 95 dB: 4 hours
• 100 dB: 2 hours
• 105 dB: 1 hour
• 110 dB: 30 minutes
• 115 dB: 15 minutes

NIOSH Recommended Exposure Limits (REL): Uses a 3 dB exchange rate (more conservative).

• 85 dB: 8 hours (the reference level)
• 88 dB: 4 hours
• 91 dB: 2 hours
• 94 dB: 1 hour
• 97 dB: 30 minutes
• 100 dB: 15 minutes

Dose formula:

• OSHA: Allowed hours = 8 / 2^((dB - 90) / 5)
• NIOSH: Allowed hours = 8 / 2^((dB - 85) / 3)
• Dose % = (Actual hours / Allowed hours) × 100

100% dose = maximum safe exposure. Above 100% means hearing damage risk.

Why two standards that disagree? OSHA’s limits are a legal floor set decades ago and use a 5 dB exchange rate, meaning the allowed time halves for every 5 dB. NIOSH’s are health-based recommendations using a 3 dB exchange rate, which matches the actual physics: sound energy doubles every 3 dB, so 3 dB really should halve your safe time. The gap is why a workplace can be legally compliant under OSHA yet still risky by NIOSH’s stricter, more scientifically grounded view.

Decibels are logarithmic, and that’s the part people underestimate. Every 10 dB is ten times the sound energy and sounds roughly twice as loud, so 100 dB isn’t “a little more than” 90, it carries ten times the energy and burns through your daily dose ten times faster. A rock concert at 105 to 110 dB can hit your full daily limit in minutes. The damage is also cumulative and permanent: noise dose adds up across everything you do in a day, the mower, the commute, the earbuds, and the hair cells lost in the inner ear don’t grow back. That’s the real case for hearing protection, since you can’t undo it later.