Application guide
How Loud Is Too Loud at Work
Two different limits are in circulation, they use two different arithmetics, and the gap between them is large. Here is what each one says, what the numbers on a meter mean, and what a phone can honestly contribute.
Exposure figures are part of the one time Pro unlock and are informational only.The limits
NIOSH and OSHA do not agree
NIOSH recommended exposure limit
The US National Institute for Occupational Safety and Health recommends keeping exposure below 85 dBA averaged over eight hours, using a 3 dB exchange rate: every 3 dB louder halves the time you may be exposed.
Source: CDC, Understand Noise Exposure.
OSHA permissible exposure limit
The Occupational Safety and Health Administration sets a legal limit of 90 dBA over eight hours with a 5 dB exchange rate, and requires a hearing conservation program once an employee is at or above 85 dBA as an eight hour time weighted average.
Source: OSHA, Occupational Noise Exposure.
The practical field test both agencies repeat: if you have to raise your voice to be understood by somebody an arm's length away, the noise is probably in the range worth measuring.
The vocabulary
LAeq, TWA and dose
A meter that only shows the instantaneous level tells you almost nothing about a shift. Three derived numbers do.
- LAeq
- The A weighted energy equivalent level. The steady level that would carry the same sound energy as the varying one you measured. It is computed as ten times the base ten logarithm of the mean of the levels converted back to energy, so a few loud minutes weigh far more than a long quiet stretch.
- 8 hour TWA
- Your measured LAeq scaled to a full shift: TWA = LAeq + 10 log10(duration / 8 hours). Measure 95 dBA for one hour and the eight hour average is about 86 dBA, because the other seven hours are assumed quiet.
- Daily dose
- The share of the recommended daily limit used up. allowed = 8 h x 2^((85 - LAeq) / 3) and dose % = 100 x duration / allowed. One hundred percent is the NIOSH recommended limit, not a guarantee of harm below it.
dB Decibel computes all three with the NIOSH criterion and the 3 dB exchange rate, and labels them informational everywhere they appear. Below 80 dBA it reports no practical time limit rather than a number.
| Sustained level | Time to 100 percent dose |
|---|---|
| 85 dBA | 8 hours |
| 88 dBA | 4 hours |
| 91 dBA | 2 hours |
| 94 dBA | 1 hour |
| 97 dBA | 30 minutes |
| 100 dBA | 15 minutes |
| 103 dBA | 7 minutes 30 seconds |
The honest part
A phone is not a dosimeter
An occupational noise assessment is done with a body worn dosimeter or a certified sound level meter, checked against a field calibrator before and after, positioned in the hearing zone, by somebody competent to interpret it. A phone in your trouser pocket measures your trouser pocket. A phone on a workbench measures the workbench.
There is also a ceiling problem. Phone microphones saturate well before an impact tool or a compressed air line does. When that happens the level shown is an under reading, not an over reading, which is the dangerous direction to be wrong in. dB Decibel raises a clipping flag in that situation instead of quietly reporting the lower number, but a flag is a warning, not a measurement.
Use a phone to find out whether a room is worth measuring properly, to compare one machine against another, and to notice that a corner of the shop is louder than everyone assumed. Then have it measured properly.
What this app is not. Readings are approximate (±dB) and come from an uncalibrated phone microphone. dB Decibel is an environmental sound measurement tool. It is not a certified sound level meter, not a dosimeter, not hearing protection and not a medical device, and it is not suitable for occupational, regulatory or legal compliance. That wording is taken from the disclaimers inside the app itself. Nothing on this page is legal or occupational health advice, and a reading from this app cannot demonstrate compliance with any regulation.
Related measurements
The same exposure arithmetic explains how quickly a concert uses up a day. If the problem is noise where you sleep rather than where you work, start with measuring bedroom noise at night.
Get the app
Find out what your workplace sits at
The free version gives you live dB(A), the session minimum, average and maximum, and Leq, L10 and L90, which is enough to compare rooms and machines. LAeq, the 8 hour TWA and the daily dose percentage are part of the one time Pro unlock, and are informational.
Free to download. iPhone, iOS 18 or newer. Optional one time Pro unlock, no subscription.Keep reading