"I always understood 120db to be the point where hearing damage occurs"
Please everybody... learn and live hearing protection. I'm 51 and have "severe" hearing loss.. ok ok Vietnam, loud rock shows, loud car audio, bad genetics but no matter how you get there.. hearing loss sucks.
In the 2 hours of a concert.. some hearing damage occurs at anything more than 91... I have foamies.. 25db custom molded "musician" earplugs... As well as the industrial strength aids I wear the rest of my life. If your ears ring after a concert... YOU have (to some degree) damaged your ears and worsened your hearing.
Whats in your ears? Decibel Exposure Time Guidelines
Accepted standards for recommended permissible exposure time for continuous time weighted average noise, according to NIOSH and CDC, 2002. For every 3 dBs over 85dB, the permissible exposure time before possible damage can occur is cut in half.
Continuous dB
Permissible Exposure Time
85 db 8 hours
88 dB 4 hours
91 db 2 hours
94 db 1 hour
97 db 30 minutes
100 db 15 minutes
103 db 7.5 minutes
106 dB 3.75 min (< 4min)
109 dB 1.875 min (< 2min)
112 dB .9375 min (~1 min)
115 dB .46875 min (~30 sec)