Electronic static sound coming out of headphone jack?

[InuNacho]

I've noticed that on my Mac Pro I've noticed that there is strange electronic high pitched alternating sound that seems to come and go when there is no other audio coming out of the jack. If I'm just working away with no music or anything, I can hear it but the second I adjust the volume or play something it vanishes.
This only affects the front jack and doesn't seem to happen on the back. Is there any reason to be concerned or is this a regular thing?

 

[Kris Kelvin]

The same thing happened on my MacPro4,1, probably because of insufficient electromagnetic shielding of the audio circuits. As long as it is very faint, I'd consider it normal.

 

[splifingate]

I get a local radio station (of unknown mHz) playing through my back line-out when the Volume is loud enough

 

[Dr. Stealth]

Ha.... I used to live by a Ham Radio nut with a HUGE antenna and I'm sure illegal amplifiers. We used to hear his voice on almost every electronic device in our home. But, what really blew me away was one morning when my wife and I were in our kitchen making breakfast his voice was coming out of our $10.00 toaster !! Absolutely true, we both heard it perfectly clear for several minutes.

 

[InuNacho]

Cool, glad its nothing to be worried about. Thanks all.