Its in the DSM criteria that people with AS/HFA often have difficulty regulating the volume of their voices.
Wikipedia wrote:
Although individuals with Asperger syndrome acquire language skills without significant general delay and their speech typically lacks significant abnormalities, language acquisition and use is often atypical.[5] Abnormalities include verbosity, abrupt transitions, literal interpretations and miscomprehension of nuance, use of metaphor meaningful only to the speaker, auditory perception deficits, unusually pedantic, formal or idiosyncratic speech, and oddities in loudness, pitch, intonation, prosody, and rhythm.
I spent three decades making a living with my voice and its pretty well trained in most respects, but when I get animated and excited talking about something, especially one of my obsessive personal interests, I find myself overemphasizing and nearly shouting before I realize its happening.