Hyperacusis is a decreased tolerance to sound. This rare auditory disorder causes many day-to-day sounds, even conversation, to be intolerably loud. Current researchers suspect that the source of the problem lies in the lower parts of the brain that control the nerves in the inner ear. In a normal person, when sounds are soft (or absent), the brain causes nerves in the inner ear to actually
amplify external sound--we're born with biological hearing aids! Normally, those nerves stop amplifying when moderate or loud sounds reach the inner ear.
In a hyperacusic patient, they seem to continue to boost the inner ear's sensitivity, regardless of the sound level.
One can think of the effect on the eyes if the pupils were to open as wide in bright sunlight as they do in a darkened room. (There is, of course, one important difference. Open pupils in bright sunlight will eventually damage the retina. Hyperacusis does not damage the inner ear, though at times the results can be downright painful.)
A modification of tinnitus retraining therapy, also known as habituation therapy, or the Jastreboff method, is highly effective in treating this condition in most patients.
The California Tinnitus Center also has available a hyperacusis instrument. It is, in effect, a reverse hearing aid. The potential advantage of such an instrument is tremendous. Because the instrument does such an excellent job of controlling the loudness of sounds, the hyperacusic patient might well be able to function normally in normal employment and social situations.