I think in some this can be an attribute of sensory overload, but it's case by case. I have excellent hearing, until I try to focus on what people are saying in conversation. It seems like when I am blocking people out that I wish I could hear and understand, that I can acutely hear other noises specifically, as they become isolated in the processing. I can also totally block someone out who is talking to me directly, but it depends on what I am doing, and type of voice they are using. I don't respond well to low tones, soft pitch, and monotone inflection. Some people consider themselves sane for speaking in this manner, but it makes me feel mentally ill.