It deals with brain function, not cochlear anatomy. Since hyperacusis is a disorder of brain function, TRT is well-suited to hyperacusis treatment. With respect to hyperacusis, the low level sound is employed to desensitize the auditory system, a system which is over-sensitive in that there is discomfort out of proportion to damage at various sound levels. Note that desensitization of an auditory system in which the threshold for discomfort approximated the threshold for damage would be deleterious. 7 Such is not the case, however, with hyperacusis.
Neurophysiologically desensitization is extremely complex.
Assume that normal environmental background sound levels are approximately 25dB. This level typically is well-tolerated by individuals with and without hyperacusis alike. It might be the sound in a fairly innocuous home setting, the kind of background sound level which would not even be apparent unless one purposely focused attention upon it. Thus, it would be a sound level routinely typically habituated by one and all. An 80dB sound would cause great discomfort to this individual, whereas someone without hyperacusis would typically be able to tolerate a level of 100dB or even possibly greater without difficulty. After several weeks, therefore, that person's brain would equate a level of 30dB with background environmental sound.