Sony Ericsson

Im so exited I got mine today in Glendale Ca. for 50% off because I have the Walt Disney Company business discount. This phone rocks,rocks,rocks. But I do have a question does anybody know if when taking video if sound is supposed to be herd from the phone itself when playing the video back? I can hear the sound but only when I play videos on
the computer. Any help would be nice. Thanks.