The most recent occurrence of this was in the University Center two days ago, when I was grabbing a deliciously unhealthy egg and cheese based breakfast. A woman approached me, and, assuming she was talking to someone else, I didn't pay much attention to what she was saying, and continued in my business. I then heard her say "Oh, I'm sorry!" in a rather loud voice. That caught my attention. I turned around, and said "Sorry for what?"
Woman looked like she had seen a ghost or something, and said, "Wait, aren't you deaf?"
"Uh... No I'm not." was my reply. "Wait, I thought you were!" At that point, I just shook my head and made a beeline for the cash register. If I weren't so used to it at this point, I would have been weirded out.
I've asked around if there is a way I act or move or speak which is distinctly different from the mannerisms of hearing people. I've been told that I speak louder than average, that I don't enunciate very well in particular situations, and that my infliction is different from that of the average person.
Well yes. Somewhat stilted speech, louder than average, those are typical of some people with autism. But I also react to noises outside of my visual range, and don't use ASL or wear a hearing aid. It still strikes me as curious that I am presumed to be deaf first rather than autistic.
But then I realized something: Deaf people aren't exactly given a strong presence in mass media, but the signs of deafness in adults are generally known to the general public. These signs overlap in autistic adults, but are rarely given time as signs of autism in TV portrayals of it, with the exception of Temple Grandin, the movie, where Temple spoke with a loud voice with very little lilt, and didn't convey much subtle nuance or emotion with her voice. Apart from that though, it's very rare to see a portrayal of an autistic adult with mannerisms like mine. No wonder deafness is the first thing that comes to people's mind!
And for those of you, like dear Elesia over at Aspietude!, who are deaf and autistic: Does someone assume you possess another disability entirely? :-P