If you are in UK, and it's coming over the radio and TV, you can ask the radio regulatory section of the GPO (or whatever it is called these days!) to investigate, as it is a (probably illegal, although probably unintentional) radio transmitter. Check with the Post Office to see what they call that department these days.
Don't mention the computer sound system to them though, or tape deck/CD player etc as these are not
supposed to recieve radio and the "fault" is in the "incorrrectly receiving" device.
(it's not coming from a mobile phone blocker by any chance is it
)