I have had a Dell Dimension 8250 for several years, and I have connected to it a set of speakers through which I listen to the radio whilst online. I am receiving a faint but audible music channel, which I can hear whether I am connected to the net or not.
Jon Godfrey
This seems to be a common example (to judge by a Google search) of radio frequency interference or RFI, though it's not something I've heard on a PC. The speaker wires may be acting as an aerial and picking up a radio signal, which you then hear from the speakers. The loudspeakers may also be implicated: some models seem to have better shielding than others.
You could try moving the speaker and mains cables, and folding up (rather than coiling up) any spare bits of wire, or changing to shorter, better-quality shielded speaker cables. If that doesn't work, try adding some ferrite rings to the speaker and mains cables. KSL Consulting has a web page, Solving Radio Interference (RFI) on Computer Speakers, which says:
"Bunching the cables with cable ties to reduce their length will reduce the interference, as will winding each speaker cable around ferrite rings (winding at least 10 to 15 turns around the ferrite ring). The ferrite rings act as RFI filters, making the cables inefficient aerials. This reduces the level of the radio signal on the amplifier wiring. Ferrite rings can be purchased from Maplin.co.uk under stock code QT26D."
Maplin and similar stores also supply clip-on ferrites and shielded cables.
Note that Cat5 Ethernet cables can also act as aerials and deliver a radio signal to the PC motherboard.
Ferrite rings are a cheap solution, if they work. Upgrading the speakers is a more expensive option.
America's Federal Communications Commission (FCC) published the useful Interference to Home Electronic Entertainment Equipment Handbook, which you can find online "preserved by KYES TV". It covers both radio and TV interference.
