iPhone Docked Playing Through PC, Buzzing

Question

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.

Any ideas?

EDIT

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.

Answer 1

There may be a second problem besides audio interference from wifi and GSM: a ground loop. This is pretty common with audio gear, and a giveaway is the buzz or hum is about 60 hertz. Once you've heard it, you'll recognize it in the future.

Answer 2

Putting the iPhone into Airplane Mode should reduce the buzzing slightly. The problem is with the cellular/Wi-Fi signals causing interference with the audio. Unless the specific accessories you use with your iPhone are labelled as "works with iPhone", they're not guaranteed not to produce the buzzing. (For instance, I have a clock radio with a dock connector, and when I connect it, my iPhone offers to turn on Airplane Mode to reduce audio interference).

Answer 3

The buzz is GSM cell phone interference.

When I first got my iPhone my co-workers speakers in the next room would not stop buzzing. The solution he got new speakers.

MacLife suggests attaching ferrite beads to your cables to prevent interference. http://www.maclife.com/article/iphone_buzz_kill