first thing first do you use the TV speakers or a reciever with surround sound
if you use the TV speakers then it is a problem with the TV if you are useing the orginal XBOX cords or someother composite audio and video then that could be the problem if your TV supports the Component Video then get those and that might solve the problem
If you are using the reciever for sound then it is most likley the audio only problem
when the XBOX or anything that transmits a signal like all white screen then it must put the max bandwith through the cables to the TV and since M$ has shitty cables then it is possable that it cant probuce the high bandwith neaded to produce a white image to make a white image the TV must turn on all the pixcles to full it is not really white it is RED GREEN BLUE mixed to make WHITE then the shity cables cant do that and some of the audio and video cross signals because it isnt properly shielded