DecibelwerkHow the calculator works
Both agencies start from a level that is acceptable for an 8-hour day and then trade loudness against time. The difference is how fast they trade:
- NIOSH: 85 dBA averaged over 8 hours, 3 dB exchange rate. Every 3 dB above 85 halves the safe time: 88 dBA 4 h, 91 dBA 2 h, 94 dBA 1 h, 97 dBA 30 min, 100 dBA 15 min.
- OSHA: 90 dBA for 8 hours, 5 dB exchange rate. Table G-16: 92 dBA 6 h, 95 dBA 4 h, 97 dBA 3 h, 100 dBA 2 h, 102 dBA 1.5 h, 105 dBA 1 h, 110 dBA 30 min, 115 dBA 15 min or less. A hearing conservation program is required from an 85 dBA 8-hour average (the action level). Impulse noise should not exceed 140 dB peak.
The safe time is 8 hours divided by 2 for every exchange-rate step above the starting level. Your dose is the time you spent divided by that safe time. Add up the doses from each part of a day to get the total; 100% is the limit.
Typical levels to try
| Level | Typical source |
|---|---|
| 70 dB | Traffic, vacuum cleaner |
| 80 dB | Alarm clock |
| 90 dB | Lawn mower, power tools |
| 100 dB | Snowmobile, earbuds at full volume |
| 110 dB | Concert, car horn, sporting event |
| 120 dB | Jet plane taking off |
| 130 dB | Jackhammer, ambulance siren |
| 140 dB | Fireworks, gunshot |
These come from the American Academy of Audiology noise chart. Real levels depend on distance and the specific source; if you want the real number for your room, your mower or your gig, measure it.
What to do when the dose is over 100%
Every 3 dB you take off doubles the safe time, so small changes matter. Step back from the speaker or machine (doubling your distance outdoors cuts roughly 6 dB), take breaks somewhere quiet, and wear earplugs or earmuffs. The NIDCD's advice: a daily average of 70 dBA or lower is safe for most people, and you should protect your ears at 85 dBA and above. More in how loud is too loud.