High pitched whine from xFi Gateway 3rd Generation box

I am getting an extremely annoying high pitched whine from my newly installed xFi Gateway 3rd Generation box.  The sound is intermittent - comes and goes but can last for at least minutes at a time.  I can make it happen by making or receiveing a phone call on my Comcast landline - as soon as the destination phone starts to ring the high pitched sound starts on the xFi box. It may stop when the call is disconnected or it may not.  It may start on its own without the phone in use, but can be reliably started by making or receiving a call.  Simply pressing a key on the phone without completing the full dial may cause the sound to modulate, and may or may not cause the sound to stop.  I have verified with family members that I am not crazy - they hear it too.  Any suggestions other than returing the box and trying my luck with a replacement?