I don't know if this is an exclusive Asperger thing or not. Certain places it's hard to tell how much your voice carries. I began talking louder when I met my husband-- he doesn't give a lot of feedback when someone's talking to him. I'm usually nodding, looking at them, saying 'uh huh'. He can be looking away or doing something else and it would drive me crazy, I'd stop talking..he'd look at me and say, 'I'm listening' ..not sure that's still the case after all these years