Audiovox SMT 5600 / SPV C500 (HTC Typhoon)

I just purchased a SMT 5600 online and am getting some kind of intermittent clicking/buzzing interference through my computer's speakers. It is definitely from the phone since the further away I place the phone the softer the sounds are. The phone orientation has an effect as well. The speaker volume knob does NOT have an effect nor does it prevent the sounds. They also happen whether or not my phone is connected via USB data cable. The sounds occur every 10-15 minutes. Does anyone have any ideas as to the cause? Thanks for reading!