If the pitch of a guy's voice goes up, does it mean he likes you?

I like a guy from work and I think he likes me...we have funny conversations etc. He goes hot and cold though; sometimes we have these great conversations and then suddenly he pulls away and goes quiet as if he's annoyed at me. I know he isn't seeing anyone. I rang his mobile on my day off and when he called me back he sounded really nervous to me. His voice was really high pitched and his voice kept breaking. He was giggling at my stupid jokes that weren't even funny. Apart from being knocked in the balls, what else makes a guy's voice sound higher? I think it's a good sign he likes me, but just don't wanna jump to the wrong conclusion as that would be embarrassing! Thanks :)
If the pitch of a guy's voice goes up, does it mean he likes you?
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