The hearing damage criteria established by the OSHA noise regulation takes into consideration the noise level and the exposure time. An exposure to 90 dB for eight hours is considered to be safe by OSHA, but it is recommended that you always use hearing protection when exposed to 100dB or more, even if the exposure is short. The exposure is doubled for every increase of 5 dB, as defined by OSHA. (Physically the sound pressure level doubles every 3 dB). The table below will explain the relationship between noise level and exposure time.