That's a really good question!
I don't know if I had "super hearing," but I've always been extremely sensitive to sound (especially discordant noise),  and kept the volume of everything as low as possible.  I'm sensitive to light, as well.  I also have a need for larger personal space than most people.  In other words, standing in a grocery line can be quite uncomfortable if the person behind me stands too close, that sort of thing.  Seems like I read somewhere that about 10% of the population are "over sensitive," and that normal environmental stimuli is too much for them.  We are the hermits 
