Why Both Level and Duration Matter
The ear's energy budget works like a dose. A very loud sound for a short time can do the same damage as a moderately loud sound for a long time — the two factors trade off. That is why a single number ("the concert was 100 dB") tells you little about risk without the duration ("…and I was there for three hours").
Two consequences follow:
- Short bursts matter less than you might fear — a passing siren at 110 dB for five seconds is very different from a 110 dB work environment.
- Steady moderate noise matters more than most people assume — eight hours of 85 dB can accumulate real risk.
This is why the measuring guide emphasizes running thedecibel meter for the full period of interest: the average and Leq are exactly the numbers that exposure thinking is built on.
The 3 dB Exchange Rule
A 3 dB increase represents a doubling of sound energy. Standard exposure guidance (for example, NIOSH) therefore halves the permitted duration for every 3 dB increase:
Note that some other standards (notably OSHA) use a 5 dB exchange rate, which allows longer times at high levels. The numbers here follow the more protective 3 dB rule used by NIOSH, which is the basis of most modern hearing conservation guidance.
Approximate Exposure Limits
The table below summarizes the NIOSH recommended exposure limit (REL) at A-weighted levels. Values are rounded guidance, not a personal medical assessment.
| Sound Level | Max Recommended Duration |
|---|---|
| 85 dB | 8 hours |
| 88 dB | 4 hours |
| 91 dB | 2 hours |
| 94 dB | 1 hour |
| 97 dB | 30 minutes |
| 100 dB | 15 minutes |
Below 85 dBA, risk is much lower and ordinary sounds (conversation at 60 dB, a busy street at 70 dB) are not a concern for typical exposure times. The sound level chart shows where common sounds fall on this scale.
Everyday Noise vs. Occupational Compliance
There is an important difference between "noise that is loud enough to be worth avoiding" and "noise that requires a formal assessment":
- Everyday awareness: for home, leisure, and personal choices, approximate measurements are enough. If the online sound meter shows sustained levels near 85 dBA or above, reduce exposure time or use hearing protection.
- Occupational compliance: workplaces in most countries have legal limits (for example, an 8-hour average limit of 85 dBA in the EU, 90 dBA under OSHA's PEL), with exposure monitoring, hearing conservation programs, and engineering controls. These assessments must use calibrated instruments meeting standards such as IEC 61672 — a phone cannot substitute.
If your employer or a regulator asks for measurements, do not use this tool for that purpose. Use theaccuracy guide to understand why, and consult a qualified occupational-hygiene professional.
Measuring Your Own Exposure
For personal awareness, a practical approach is:
- Calibrate the meter once against a known reference for better consistency.
- Measure each noisy period you care about — commute, gym, music, workshop — for its full duration.
- Note the Leq and duration of each period (the meter records both; save to the Noise Journal or export CSV/JSON).
- Estimate your daily "dose": a period at 91 dB counts for ~2 hours of allowance; two such periods count for the full day.
- Reduce the loudest periods first — every 3 dB you shave off doubles the safe time.
Because phone readings are estimates, treat the result as a rough check, not a clinical measurement. If you regularly suspect high exposure, have your hearing checked by a professional.
Protecting Your Hearing
- Move away or reduce volume — distance is the simplest lever: doubling the distance cuts the level by ~6 dB.
- Use hearing protection (earplugs or earmuffs) for concerts, workshops, and loud machinery.
- Follow the 60/60 rule for headphones — around 60% volume for no more than 60 minutes at a stretch is common practical advice.
- Give your ears rest after loud events; ringing ears are a sign the exposure was too high.
- Consult a professional if you notice persistent ringing, muffled hearing, or pain.
Further reading: NIOSH noise and hearing loss prevention (cdc.gov/niosh/topics/noise), WHO hearing loss prevention (who.int), and OSHA occupational noise exposure (osha.gov/noise).