I just recently purchased a 2007 BMW X3 with approximately 28000 miles on it. Upon test drive, I did not hear the high pitched (and quite loud) humming sound coming from the front of the vehicle when driven specifically between speeds of 35 to 42 miles per hour. Strangely, this noise is not audible at lower speeds or speeds exceeding 45 mph. Also, when breaking to a stop from speeds greater than 45 mph, the noise is VERY noticeable just between the speeds indicated above. I took the vehicle for a service check but the BMW technician concluded this was a trait of the vehicle's engine. I cant imagine this to be the case considering how loud it sounds and the fact that I have been unable to find any other 07 X3 owner with a similar complaint. I am quite frustrated with this and can't imagine BMW building an engine with such a flaw. I know this vehicle has transmission issues but no such problem is experienced when I drive it. Does anyone have any ideas about this and how I should handle this problem?