[X3Viking]

Hi all,
My X3 2,5 2004 sends out a distinct vibrating sound at specific speeds. The noise appears louder when slowing down compared to accelerating. It started very low a year ago but the BMW dealer could not give me a recommendation on what to do. Last week the noise suddenly became a lot stronger.
Anyone recognize the symptom or having any idea what could cause it?

Thanks in advance/ME