I'm asking here first before I take it in to an Audi dealership service..Recently I've just noticed a low pitched hum that sounds like its coming from the left side, possibly from the front wheel area, and it starts at around 80mph, and continues to about 90, then gets a little quieter. I hear nothing up until right around 79-80, then it starts in. Usually that means a tire or bearing issue that kicks in at a particular speed to trigger it, but I'm not sure, maybe I'm wrong. The tires have plenty of tread, and I haven't had any issues with suspension. Has anyone on here experienced this and if so what was it? Thanks for any help!