Repeated exposure to loud noise fatigues the hair cells in the inner ear. Just like the reeds, some of these hair cells will return to the normal position, but others will have been damaged beyond the point of recovery. The destruction of these hair cells is evidenced by permanent hearing loss.
Noise induced hearing loss typically occurs gradually and without pain. Often by the time a person realizes that there may be a problem, it is too late. But there are early warning signs.
How Loud Is Too Loud?
Loudness is measured in decibels (dB). Experts recommend that you use earplugs when exposed to 85 dB and above. The following list shows common sounds and their approximate dB levels.
20 dB: Ticking watch
30 dB: Quiet whisper
40 dB: Refrigerator hum
50 dB: Rainfall
60 dB: Sewing machine
70 dB: Washing machine
80 dB: Alarm clock (two feet away)
85 dB: Average traffic
95 dB: MRI
100 dB: Blow dryer, subway train
105 dB: Power mower, chain saw
110 dB: Screaming child
120 dB: Rock concert, thunderclap
130 dB: Jackhammer, jet plane (100 feet away)
Exposure to once-only or continuous noise can cause hearing loss. If hearing recovers, this loss is called temporary threshold shift, which typically disappears after 16 to 48 hours.
Hearing loss can be permanent if loud sounds damage the cells in the inner ear called cilia. Once damaged, these cells cannot be repaired.
SOURCE: American Tinnitus Association