Hi John, what device is making the "chugga-chugga-boom-boom" sound? Is it the TV or the Contour receiver itself? Another way to diagnose this would be to swap the receiver out for another one in the home. If the issue corrects itself, then this could indicate a problem with the receiver. Please ensure all connections, including the HDMI cable, are tightly secured and do not contain any damage.
Also, do you have a soundbar or another piece of audio equipment? -Kevin M. Cox Support Forum Moderator