On several websites, hyperacusis is defined as the “loss of the ear’s dynamic range, understood as the auditory system’s ability to handle rapid increases in sound volume.” At first, I didn’t take this definition very seriously because hyperacusis is, above all, a reduction of the maximum tolerable intensity. Clearly, my problem was excessively loud sounds, which previously were no issue and now were intolerable, and I didn’t notice any particular difficulty with rapid volume changes.
However, over time I realized that this definition is incomplete. In hyperacusis, the limitation is not only the maximum tolerable sound intensity but also sudden variations in volume. This means that sounds with an intensity clearly within our comfortable range can still be incomprehensibly difficult to tolerate. For example, a person with hyperacusis might tolerate the noise of a bus at 75–80 dB without difficulty, yet a door slamming at only 65 dB—if heard in a very quiet environment—can leave the ear somewhat sore and more sensitive.