It started two months ago, but it still annoys my dad and I. Whenever we are on the freeway accelerating faster, maybe up to 75, there is a buzzing noise coming from the front. We got worried, so we took the x5 to the dealership to check it out. They didn't know either. It happens a lot. Is there something wrong? I told my dad it was the wipers buzzing, but can't make a final verdict. What do you guys think?