This can be affected by medications. It can also be affected strongly by salicylates. Salicylates occur in aspirin, and also in a large number of fruits and vegetables. So if you eat a lot of fruits and vegetables, your hearing will temporarily change until the salicylates have gotten out of your system. It can also be triggered by substances that you get on your skin, but that's another long and complicated subject that I don't feel like getting into. My hearing sensitivity changes noticeably when I've been eating salicylates.