If it's coming through the radio I doubt it will say anything on the dash,it has nothing to do with it,if you take a mobile phone in the car I would look to that(new phone/new holder position)the radio has nothing to do with the running of the car,seems like the radio is picking up a signal from something(sat nav maybe).If it has just started and you have a new gizzmo in the car switch it off and see if the noise stops.
Rich, January 2010