Hyperacusis is commonly defined as a heightened, abnormal sensitivity or intolerance to ordinary, everyday sounds that would not bother most people. That means what may sound normal and completely acceptable to you may be perceived as outrageously LOUD and painful to me. People who experience hyperacusis (about 8-15 percent of the general population) often also have tinnitus (ringing in the ears).
Hyperacusis affects people to varying degrees, from mild to severe, and is different than phonophobia (fear of sound) or misophonia (dislike of sound) which usually involve emotional response to specific sounds. People with hearing loss who experience loudness recruitment (an abnormal growth in the perception of loudness) may also experience hyperacusis, but not always.
Although hyperacusis has many known causes and associations, most cases have no known cause. A few diseases and syndromes that are associated with hyperacusis, include migraine, depression, post-traumatic stress disorder, head injury, Lyme disease, Williams syndrome, fibromyalgia, Addison’s disease, autism, myasthenia gravis, and middle cerebral aneurysm. Research suggests that hyperacusis may also be associated with multiple sclerosis.