## How long can a person endure a certain noise level before hearing impairment occurs?

 One way that noise can permanently damage your hearing is by a single brief exposure to a high noise level, such as a firecracker going off near your ear. But hearing damage can also occur gradually at much lower levels of noise, if there is enough exposure over time. To protect your hearing, you'll want to limit your exposure to these moderately high noise levels as well, and give your ears a chance to recover after any period of noise exposure.

## Calculate SPL

 Permissible time   Seconds Minutes Hours

## Calculate Time

 Permissible SPL  dB

 Accepted guidelines for recommended permissible exposure time for continuous time weighted average noise, according to NIOSH-AINSI and CDC. For every 3 dB sound pressure level (SPL) over 85 dB, the permissible exposure time is cut in half − before damage to our hearing can occur. NIOSH = National Institute for Occupational Safety and Health. CDC = Centers for Disease Control and Prevention. OSHA = Occupational Safety and Health Administration. NIOSH represents the use of an 8-hour exposure of noise at 85 dBA and a 3 dBA doubling rate, to determine the noise dose. OSHA represents the use of an 8-hour exposure of noise at 90 dBA and a 5 dBA doubling rate, which does not protect many workers from hearing loss over their whole working lifetime.

## Permissible Exposure Time Guidelines

 Sound Pressure Level Sound pressure Permissible Exposure Time 115 dB 11.2 Pa 0.46875 minutes (~30 sec) 112 dB 7.96 Pa 0.9375 minutes (~1 min) 109 dB 5.64 Pa 1.875 minutes (< 2 min) 106 dB 3.99 Pa 3.75 minutes (< 4 min) 103 dB 2.83 Pa 7.5 minutes 100 dB 2.00 Pa 15 minutes 97 dB 1.42 Pa 30 minutes 94 dB − − − − − − − − − − 1.00 Pa − − − − − − − − 1 hour − − − − − − − − − − − 91 dB 0.71 Pa 2 hours 88 dB 0.50 Pa 4 hours 85 dB 0.36 Pa 8 hours 82 dB 0.25 Pa 16 hours

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