While listening to music, I notice sometimes that I've turned up the volume on my iPod too loud. I can actually feel the damaging effect that loud music can have on one's eardrum. The book talks about conductive deafness, which is due to a malfunctioning of the ear, especially a failure of the eardrum or the ossicles of the inner ear. My friend's brother has this case of deafness, so I know a little bit about it. His pitch perception is close to being useless because his hair cells located in the basilar membrane are not working.
Humans have a hearing threshold. This is the minimum sound level of a pure tone that an average ear with normal hearing can hear with no other sound present, (Johnson, 5). The hearing threshold (and the hearing ability of the individual all together) can be impaired due to damaging frequencies of sound like listening to an iPod too loud. There has been some discrepancy about whether or not the eardrum can be damaged from an iPod, but I will most likely be turning my music down after learning this information.