At work I do everything at my desk, am seldom disturbed and don’t really use the phone, so I’ve always got one headphone in and Xfm on the Radio (Keavney’s a legend). My headphones are of the kind that loop round and over your ear, and they’re white (white being cheaper than black for some mental reason).
One day, my radio ran out of batteries, and rather than sit like a spanner with one earphone in, I removed it.
On going into the kitchen, everyone started speaking very loudly and gesturing hugely.
Turns out they all thought I was deaf in one ear and that my headphones were a hearing aid.
Emsbabee
Pro 
Ah, but it can always be worse. I used to work at a day centre for people with learning disabilites, and got mistaken for a service user on more than one occasion. I probably should have taken advantage and got a good parking space out of it.