My XM base unit in my house has developed a high-pitched ringing sound that comes through the speakers of my stereo system. It doesn't do it in the car, only in the house. I have switched radios and base units (my husband and I each have one), and it still rings. I have turned off the stereo and turned on the xm radio and the ringing is definitely from the xm unit itself. It also happens on all the radios in the house.