AC/DC have postponed their US tour after singer Brian Johnson was warned by doctors that he was at risk of "total hearing loss". This is unsurprising, given the decades that the Australian band has been pumping out the hard rock decibels . But deafness isn't only a concern for rock musicians. In recent years it has become clear that anyone around music a lot has reason to be equally worried. When exposed to music, risk to hearing arises from a combination of how loud the sound is and how long you're exposed to it. If you visit a nightclub that is thumping out  music on the dance floor at 100 dB, then after only 10-15 minutes the exposure is potentially damaging. In a quieter part of the club, but where the music is still loud enough that you have to shout at your friends, then you could be there for a couple of hours before having to worry about your hearing. Of course music frequently exceeds 80-85 dB, but what counts most in assessing the risk to hearing is the average exposure. Exposure to high noise levels often causes temporary deafness - something many people have experienced after going to a nightclub. While hearing usually recovers after a few hours or days, repeated loud exposure leads to permanent hearing damage. Initially, this damage is subtle and unlikely to be noticed by the listener. Problems only becomes significant in middle age when the noise-induced hearing loss combines with the natural loss of hearing due to ageing. Improved technology means that the number of musicians having to give up performing could decrease, but student musicians need to be educated about the dangers of noise-caused hearing loss. The increasing use of headphones will also work against this - for musicians and everyone else. Unless people are careful with the volume level on their portable music players, hearing loss caused by music will increase. (http://theconversation.com/highway-to-hearing-hell-musicians-and-the-danger-of-deafness-55983) What's the most important factor considered in the assessment of risk music has to hearing?
Its decibel. The average exposure. Its playing environment. The listener's sensitivity to sound