Weird, this is going to sound silly but does it still do it when the system is offline? Are your external speakers USB input? If externals are USB, try unplugging the internal speaker and see if there is any effect. If the audio issue persists offline I would suggest that it could be an issue with the internal ground connection related to audio and that your system may be acting as an FM receiver, sounds goofy but I HAVE seen this happen, though rarely.
I have Cambridge Soundworks speakes.
I get random chinese sounding men talk audio comes through them.
Sometimes even when I unplug speakers from my PC.
I can post thae audio bytes. But I don't know how to post audio file here.
Please let me know, if you have any ideas.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic