I have used Z1 for few months. I have heard high pitch sound from the PJ that come for a while about 2-3 min then it quiet for 15-30 min and it come back again. This sound come and go by cycle like this. I asked the technician from Sanyo distributor. He said that sound was normal. It was in the normal specification of this PJ. It came from The Ballas lamp was charging high frequency voltage. I think this sound is so annoying to me. So I would like to ask anyone who use this PJ that do you hear this sound like me. For me to be sure that the sound is normal function of this PJ.