How many hours per day can you be exposed to a noise level of 90 dB?

• A. 8 hours
• B. 4 hours
• C. 2 hours
• D. 1 hour

Answer: (A)

Exposure to loud noise is governed by how long you can be exposed at a given sound level. The louder the level, the shorter the safe exposure time. This uses a 5 dB exchange rate: for every 5 dB increase, the permissible exposure time is reduced roughly by half. At the specified noise level, the standard rule allows exposure for the duration of a typical workday without hearing protection. If the level increases a bit more, the allowed time would shrink to about half of that, and so on. Wearing hearing protection changes the effective sound level and can extend the safe exposure window according to the protection it provides.