High-Pitched

What is it with girls and high pitched noises? Now apart from the obvious anatomical differences, that female voice-boxes are generally structured in much smaller proportions, I am talking about the random noises females emit. When ever a girl is laughing hysterically, sees someone they really like/haven't seen "for-like-evar!" or are saying "you're welcome" somehow or is general excitement, their pitch slides up a few notches, and in some cases results in an incredibly irritating noise. I will be the first to admit my guilt. In particular, I remember a time when a girlfriend and I were discussing some hilarious topic, and the boys around us stared as our speech became unintelligible, which they dubbed "speaking in squeak." Luckily, females alike are able to decifer the high pitched noises, but really. What's up with that?