[DuncanM]

Interestingly enough I had the same thing happen the other day on my C43. I was on the parkway going about 70 and traffic was stopping infront of me. I applied the brakes lightly as I was pretty far from the slowdown. I heard the sound you described and turned down the radio as I thought that was the source but the sound persisted. Once I got <10mph I let the brakes off altogether and the sound stopped. It hasn't done it again. The car was dry and the road was dry. It sounded like it was coming from the rear of the car but it did not sound like anything I've heard brakes do.