Decibel Shield
OSHA noise limits › Noise dosimeter
Noise dosimeter: your running noise dose
Start the dosimeter and leave this page open while you work. It measures the A-weighted level ten times a second and adds up your noise dose under two rules: NIOSH (85 dB(A) for 8 hours, halving every 3 dB) and OSHA (90 dB(A), halving every 5 dB). 100% is a full day's limit. It is an estimate, not a certified dosimeter.
- Measured for
- 0:00
- Average (Leq)
- --
- Maximum
- --
- NIOSH dose so far
- 0.0%
- OSHA dose so far
- 0.0%
- At this pace for 8 hours
- --
An estimate from your device's microphone, not a certified dosimeter: like every browser meter, readings are within roughly ±10 dB (see how accurate is it), and because the NIOSH dose doubles every 3 dB, treat the percentage as a guide to whether a day is likely to be a problem, not a measurement of it. It only counts time it can hear: keep this page open with the screen on (it asks the browser to keep the screen awake), because a locked screen or another app in front pauses it. Levels below 80 dB(A) add nothing to either dose. Nothing is recorded or uploaded.
Last updated:
How long each level is allowed
| Level | NIOSH (85 dB(A), 3 dB) | OSHA (90 dB(A), 5 dB) |
|---|---|---|
| 85 dB(A) | 8 h | 16 h |
| 88 dB(A) | 4 h | 10.6 h |
| 90 dB(A) | 2.5 h | 8 h |
| 91 dB(A) | 2 h | 7.0 h |
| 94 dB(A) | 1 h | 4.6 h |
| 95 dB(A) | 48 min | 4 h |
| 97 dB(A) | 30 min | 3.0 h |
| 100 dB(A) | 15 min | 2 h |
| 103 dB(A) | 8 min | 1.3 h |
| 105 dB(A) | 5 min | 1 h |
Computed from the two rules as published: OSHA 29 CFR 1910.95 (with Appendix A) and NIOSH Criteria for a Recommended Standard: Occupational Noise Exposure (98-126). The OSHA noise limits page explains both. On phone apps: NIOSH Sound Level Meter app.
How the dose is added up
A dose rule turns every level into an allowed time. Under NIOSH, 85 dB(A) is allowed for 8 hours, 88 for 4, 91 for 2, and so on; a minute at 91 dB(A) therefore uses one part in 120 of the day. The dosimeter does that sum ten times a second, skipping anything below 80 dB(A), and shows both rules side by side. The 8-hour projection assumes the rest of the day carries on at the pace measured so far, which is the useful question at lunchtime: if this continues, where will I end up?
A guide, not a certified measurement
A workplace noise survey uses a calibrated dosimeter worn at the shoulder. A phone or laptop microphone is not that, and like every browser meter its readings are within roughly ±10 dB; because the NIOSH dose doubles with every 3 dB, the percentage is a guide to whether a day is likely to be a problem. To check a single loud moment against the limits live, use the decibel meter, and for how long common sounds are safe, the safe decibel levels guide.
What is a noise dose?
The share of a full day's safe noise you have used up. 100% is the limit: under NIOSH that is 8 hours at 85 dB(A), or any mix of louder and shorter that adds up to the same. Above 100%, the day carries more risk of hearing damage than the limit allows.
Why are the NIOSH and OSHA numbers different?
They answer different questions. OSHA's is the legal limit for US employers: 90 dB(A) for 8 hours, halving the time for every 5 dB louder. NIOSH's is the health recommendation: 85 dB(A) for 8 hours, halving every 3 dB. At any level above 85 the NIOSH dose climbs faster.
Can a phone be used as a noise dosimeter?
As a guide, yes; for compliance, no. NIOSH, which publishes its own sound level meter app, found the best iPhone apps read within about 2 dB(A) of reference equipment, and says such apps are not a replacement for a professional sound level meter or dosimeter. A browser meter is less certain still, and the dose doubles with every 3 dB of error, so use this to see whether a day is likely to be a problem, and a calibrated dosimeter when it matters.
Does it keep measuring when the screen locks?
No. Browsers stop the microphone when the screen locks or another app comes to the front, so the page asks the browser to keep the screen awake and counts only the time it actually heard. The measured time is shown, so a gap is never filled in by guesswork.
What counts toward the dose?
Every tenth of a second at 80 dB(A) or more, weighted by how long the rule allows at that level. OSHA's rule integrates sound from 80 dB(A) up, and this page uses the same floor for the NIOSH dose. Quieter sound adds nothing, which is why an ordinary office day stays near 0%.