NOISY BACK END

Mate has problem with Octy 1.9 2009 model,and asked for help but as I don't have a clue I thought maybe one of Briskoda members might know the answer- When he is driving, especially at around 50/60 MPH he gets whats he calls a " constant on/off droning noise " from back end, even gets it when he coasts along out of gear/engine switched off!( He doesn't have a habit of doing this-SO HE SAYS ).his cars done about 80K miles, any advice? :wonder:

Edited 6 October, 201114 yr by GBLAF