I have an iPhone that I fit into an Apple dock. There is an audio cable from dock into the line in on my sound card. My headphones are plugged into the line out.
I get this really quite buzz that is fairly constant, but changes as the iPhone "does stuff".
It's not so bad when the music is playing. But when it stops I get the buzz, so I can't really use my headphones as "noise cancellation."
It doesn't help to change my volume sliders on the PC.
I've been debugging this issue a bit. It actually doesn't matter if the iPhone, Dock, or Line-In are hooked up at all. So I guess its not an iPhone issue.
I don't think it's a GSM signal issue because it happens if the phone is in the other room as well.
Thanks in advance.