Decibel Levels Table
| Sound (NIDCD average) | dBA | Max daily time at top of range |
|---|---|---|
| Normal conversation | 60-70 | no practical limit |
| Movie theater | 74-104 | about 6 min |
| Motorcycles and dirt bikes | 80-110 | about 89 s |
| Headphones at max volume, concerts | 94-110 | about 89 s |
| Sirens | 110-129 | about 1 s |
| Fireworks show | 140-160 | instant - protection required |
| dBA | NIOSH max daily exposure |
|---|---|
| 85 | 8 h |
| 88 | 4 h |
| 91 | 2 h |
| 94 | 60 min |
| 97 | 30 min |
| 100 | 15 min |
| 103 | 7 min 30 s |
| 106 | 3 min 45 s |
| 109 | 112 s |
| 112 | 56 s |
| 115 | 28 s |
Decibels are a log scale, which is why the numbers mislead: every step of 10 dB is ten times the sound energy, and the NIOSH rule of thumb makes the hearing cost concrete - each 3 dB increase cuts the safe daily exposure time in half. Eight hours is the ceiling for 85 dBA; 88 dBA buys four hours; 100 dBA buys fifteen minutes; a fireworks show at 140-160 dBA is past any safe duration at all.
The table below carries the average decibel ratings of familiar sounds as the NIDCD publishes them, each extended with the exact maximum daily exposure the NIOSH 85 dBA / 3-dB exchange rule allows at the top of that range. Type any level into the box and the same arithmetic runs for your number - so a movie theater (74-104 dBA) reads as no practical limit at the quiet end but about six minutes at the loudest corner of the same room.
How to use
- Type a sound level in dBA to see its band and the NIOSH maximum daily exposure time at that level.
- Read the table for the sound in front of you - the exposure column is computed at the top of each published range, the worst case in the room.
- Halve the time for every 3 dB you add: two tools at 88 dBA together hit roughly 91 dBA, and the four-hour allowance becomes two.
Frequently asked questions
How loud is too loud for your ears?
NIOSH puts the occupational exposure ceiling at 85 dBA averaged over eight hours, and the NIDCD states plainly that repeated exposure at or above 85 dBA can cause hearing loss. The scale does the damage quietly: 88 dBA is four hours, 97 dBA thirty minutes, 100 dBA fifteen minutes. Distance and duration matter as much as the number - the NIDCD's rule of thumb is to avoid noises that are too loud, too close, or last too long.
Why does each 3 dB halve the safe time?
Because decibels are logarithmic, +3 dB doubles the sound energy arriving at your ear. NIOSH caps the daily energy dose, so doubling the energy must halve the time: the 'exchange rate'. That is why the exposure ladder below drops by a factor of two per row - 8 h, 4 h, 2 h, 1 h - while the dB column only climbs by three each step. A-weighting (the A in dBA) is the filter that mirrors what human hearing actually emphasizes.
Is 85 dB safe if I only listen for an hour?
One hour at 85 dBA sits well inside the eight-hour allowance - the ceiling is a dose, not a wall. The trap is stacking: an hour of sirens (110-129 dBA range) spends about a full day's allowance in minutes at the top of the band. The lookup handles the arithmetic so you do not have to - type the level, read the time, subtract as you go.
How loud is a fireworks show, really?
The NIDCD averages it at 140-160 dBA - the top entry in the table, and beyond any safe exposure: the ladder bottoms out near 28 seconds at 115 dBA, ten to thirty decibels before the worst fireworks. Explosions are also impulsive, which concentrates the energy; hearing protection is not a nice-to-have at a front-row show, it is the only control left once distance is fixed.
What is the difference between dB and dBA?
dBA applies the A-weighting filter, which discounts the low and very high frequencies human ears hear poorly, so readings track perceived loudness and hearing damage better than raw dB. All the ratings here - NIDCD's sound table and NIOSH's exposure ceiling - are dBA. That is also why two sounds with equal energy can carry different dBA numbers: the weighting, not the loudness war, decides.