Levels chronically above 90 to 95 will damage hearing over time. The absolute level necessary to damage hearing varies with the suddenness of onset, the time exposed, and some other factors which have not been discovered. The auditory nerve is the most highly charged nerve in the human body. On average, about twice the electrical charge of other nerves. This seems to make it much more likely to sustain damage.
Damage can occur in several ways.
Many young people, rock musicians, and rock concert devotees will have major damage to their hearing from excessive noise levels. Even excessive noise from portable earphones and Walk-Man like players can produce this problem. Consequently, whenever you are around high noise levels-guns, amplifiers, etc. use extreme caution in protecting your ears. Neurotoxins of any type or diseases that affect nerves often effect the auditory nerve. Diabetes mellitus, B12 deficiency, and any inflammatory process can also effect this nerve.