Noise Levels and Exposure Guidelines


To fully understand your audiogram and hearing aid specifications, you need to relate various sounds to the sound pressure level (SPL) in db (decibles) and the danger of loud noises to your hearing. This is why when wearing a hearing aid for the first time, always start with a low volume setting and then increase it gradually. Also the hearing aid should not output a sound greater than 130dB regardless of the input sound level.

Normal conversation is at around 50dB and this is normally used as reference input signal. A very loud sound is at 90dB and beyond, and 90dB input sound is used to test the output at the upper limit.

According to 2002 recommendation from CDC and NIOSH, continuous exposure to loud noises can cause permanent damages to your ear. The following is the accepted standards for recommended permissible exposure time for continuous time weighted average noise. For every 3 dBs over 85dB, the permissible exposure time before possible damage can occur is cut in half.

Noise Levels & Exposure Time Guidelines
Noise Level (dB) Common Sounds Hearing Sensation Permissible Exposure Time
0 Hearing threshold Not quite audible No limit
10 Rustling leaves Just audible No limit
20-30 Quiet whisper at a distance, library, very quiet PC Subdued sound No limit
35-40 Quiet office, normal PC, bedroom, sound of a mosquito, refrigerator hum Subdued sound No limit
50 Light auto traffic (100 feet), normal conversation Clearly audible No limit
60 Restaurant, air-conditioning, slightly elevated conversation Slightly intrusive No limit
70 Noisy restaurant, freeway traffic, busy office Noisy, hard to use a phone No limit
80 Vacuum cleaner, alarm clock, hair dryer Very noisy, annoying No limit
85 Average factory, electric shaver Increasing annoying 8 hours
90 Heavy truck, busy city street, lawn mower, screaming child Very loud, very annoying ~2 hours
100 Jet takeoff @ 500m, train horn @ 30m, jackhammer Very loud ~15 minutes
110 Rock concert, chainsaw, snowmobile Very loud ~1.6 minutes
120 Car horn, air-raid siren, propeller aircraft Extremely loud ~7 seconds
130 Military jet, shotgun, hydraulic press Almost intolerable None
140 Gunshot, jet engine taking off Pain threshold, intolerable None
180 Rocket launching Instant eardrum perforation None