How long a given noise level is permissible
Every 3 dB rise in noise halves the time a day can hold. Enter the level in dBA together with your actual exposure, and the page returns the permissible time, how many times over or under it you are, and the figure produced by an agency that uses a different exchange rate. A permissible time longer than a day is displayed as 24 hours or more, but the ratio is always worked out from the uncapped, unrounded permissible time.
The formula is permissible time = 8 ÷ 2^((level − 85) ÷ 3) hours (as of October 2026), because the National Institute for Occupational Safety and Health sets its recommended exposure limit at an 85 dBA eight-hour time-weighted average with a 3 dB exchange rate. Its published examples are under 15 minutes at 100 dBA and about four hours at 88 dBA. The contrast figure comes from the Occupational Safety and Health Administration, which uses 90 dBA with a 5 dB exchange rate and so allows longer at the same level.
This is an occupational exposure scheme. Recreational listening through earphones is assessed under a separate scheme that works in sound dose (Pa²h), so do not substitute this page for it. Staying inside the permissible time is not a guarantee against hearing loss, and people differ. The level should be a measured figure; a guess by ear moves the answer a long way. This result is not a medical diagnosis.
Frequently asked questions
It is how much louder the noise has to get before the permissible time is halved. A 3 dB rate halves the time every 3 dB; a 5 dB rate every 5 dB. The same noise therefore yields different limits, and the 3 dB rate is described as gaining support in national and international consensus.
That is 15 dB above the 85 dBA reference, which is five halvings at 3 dB each. Eight hours divided by 32 is 0.25 hours, or 15 minutes. The source describes this figure as under 15 minutes.
That is not guaranteed. These limits are population-level recommendations and individuals differ. Ringing in the ears, muffled sound, or difficulty following conversation are reasons to see an ear, nose and throat clinician.