Why 85 dB?
At 85 decibels, the National Institute for Occupational Safety and Health (NIOSH) determined that you can safely be exposed for 8 hours without risk of hearing damage. This is the baseline from which all hearing safety calculations derive.
Below 85 dB, you can listen indefinitely. Above it, the clock starts ticking.
The 3 dB Exchange Rate
Decibels use a logarithmic scale. Every 3 dB increase doubles the sound energy—and halves your safe exposure time.
Every +3 dB = 2× sound energy = ½ safe time
| Decibels | Safe Exposure Time | Example |
|---|---|---|
| 85 dB | 8 hours | Heavy traffic |
| 88 dB | 4 hours | Subway |
| 91 dB | 2 hours | Motorcycle |
| 94 dB | 1 hour | Lawn mower |
| 97 dB | 30 minutes | Loud headphones |
| 100 dB | 15 minutes | Club/concert |
| 110 dB | ~90 seconds | Front row concert |
"The 85 dB threshold isn't arbitrary—it's based on decades of research into hair cell damage. What many people don't realize is that damage is cumulative. Four hours at 88 dB today plus four hours tomorrow isn't 'reset'—it compounds."
How Protection Changes the Math
Quality hearing protection reduces incoming sound by 20-30 dB. At a 110 dB concert with 25 dB reduction, you're experiencing 85 dB—the safe threshold.
Without protection: 90 seconds before damage
With 25 dB protection: 8+ hours of safe listening
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