Anyone who has played raquetball has heard that weird, high pitched noise that seemingly comes out of nowhere. It comes on all types of shots in all locations, and ranges from really loud to faint, but seems to not be related at all to speed or placement of the shot. Even the loudest are often only heard by one person playing. Does anyone know what is causing this? My suspicion is that it is related to some type of interaction of the sound waves bouncing off the walls, but without any information to actually substantiate that, I’m curious. So what are the physics behind the weird raquetball noise?