Dose and Limits

Damage depends on level and duration together, and every exposure limit in the world is written as a level paired with a period. A number quoted without the period is not a specification.

When employers review noise dose alongside working patterns, learn more can provide operational context, while exposure limits still need to be assessed from sound level and duration.

A decibel is a logarithmic ratio, not an ordinary unit: 3 dB is twice the energy, decibels do not add arithmetically, and dBA is a different quantity from plain dB.

The exchange rate converts level into permitted time. Under the 3 dB rule, 85 dBA gives eight hours and 100 dBA gives fifteen minutes.

A useful external reference for further context is CCOHS noise resources.

Two US standards disagree. OSHA permits 90 dBA over eight hours with a 5 dB exchange rate; NIOSH recommends 85 with a 3 dB rate. At 100 dBA that is an eight-fold difference in permitted time, and the more permissive one is the law.

Sound does not add the way people expect: two identical sources give 3 dB more, and removing one of ten changes almost nothing.

Dose accumulates across the whole day, and because of the exchange rate one short intense activity usually dominates a total that felt moderate.

And one check needs no instrument — if you must raise your voice at arm's length, the level is likely at or above 85 dBA.

• Adding Sound

  Decibels combine logarithmically. What that means for noise control, and why removing one source of many buys almost nothing.

• Your Daily Total

  Dose accumulates across work, commute, gym and evening. How to add them, and which single activity usually dominates.

• Dose, Not Loudness

  Hearing damage depends on level and time together. Why a brief loud moment and a long moderate one can carry the same risk.

• The Exchange Rate

  The rule that converts a sound level into permitted exposure time. Two versions are in use and they diverge very fast.

• Legal and Safe

  Two US agencies publish different noise limits and the law uses the weaker one. At 100 dBA the gap is eight to one.

• The One-Sentence Test

  A free check that needs no instrument and identifies hazardous levels reliably enough to act on. Why it works.

• What a Decibel Is

  A ratio on a logarithmic scale, not a unit of loudness. Four consequences that make every other number on this site readable.