Short wave radio in background. Long analog mini-jack cable in phones jack?

Question

I couldn't find the techy/nerd discussion forum, so we'll try here. It's perhaps caused by a poorly insulated cable we bought yesterday at a big box computer and a/v store which is five meters long, but I shouldn't guess. The motherboard is huge with analog jacks at either end. I'll try a shorter cable when I'm done with this.
I'm curious how this curious phenomenon could occur, but my knowledge of radio waves doesn't go beyond history of science classes from way back when.
We heard it last night. Sometimes faint, sometimes loud. It's still there this morning, but it's very faint. Clearly a radio broadcast. The language sound like it's from far in the East in the Moslem world, which is why I guess that it's shortwave. Maybe Farsi. It's on JBL speakers. These (mac?) speakers are in three parts. The big strange dome and two tweeters. The radio station comes only through the tweeters. The odd thing is that we exchanged the cable from the big dome to the front of the mac pro. But perhaps, since the big dome is for bass, we can only hear it on the tweeters. We would have used the back jack, but the analog jack in the back doesn't work since two days (we are gentle with everything), and now sometimes we have a contact problem with the phones jack in the front. This is a brand new macpro with only OSX and FCP and updates installed, and disk permissions repaired, on a secure swiss telephone internet line.
No other radios are being used in the house. We are in the country five kilometers from our internet connection. We have two monitors connected. The Mac HD, with the out of box cable, plus a VGA flat screen Acer with about a two meter cable.
That's more than enough for the moment. I'll plug in the shorter cable and see if we still have the radio noise.

Answer 1

Ah ha! Problem solved. I unplugged our old but fancy Pioneer amp and components, and the radio station noise disappeared.
It is about three meters away. It was in standby mode. It has a tuner, but the tuner was not on.
Anyone bored enough to explain this phenomenon? I guess that it wouldn't be a bad idea to understand something about radio interference. The general public might not even notice, but for someone who is concentrating hard, it could be very distracting.