The maximum allowable noise dose is
- a sustained noise level of exactly 85 dB for eight hours.
- any combination of noise level and exposure time equivalent to 90 dB(A) averaged over eight hours.
- a continuous noise exposure level of 70 dB for eight hours.
Explanation from PART66Online
A noise dose is a time-weighted average, so it trades level against exposure time: the limit is not a single sound level but any combination of level and duration adding up to the same energy. Under the US OSHA scheme quoted here that ceiling is 90 dB(A) over eight hours, with a 5 dB exchange rate, so halving the time allows 5 dB more. Fixing a single level for a fixed eight hours, as the other two options do, ignores that trading entirely. European limits are set lower and on a 3 dB exchange rate -- the action values are 80 and 85 dB(A) with an exposure limit value of 87 dB(A) at the ear.
sparkymarky asked · 15 Aug 2016
Maximum allowable cannot be OVER 90db twa? Surely 90db twa IS the max, not something OVER this level?
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