v8 with 73k miles. At approx. 30mph a deep humming sound begins and the faster I drive the more high pitched the sound. When speed decreases the sound seems to be even louder as opposed to when I am speeding up. Ive cranked up my speed to 90mph and of course the sound becomes more higher pitched and less noticeable but only because the obvious ratios of wind speed and distance traveled per second. I thought it was my brand new POS continental tires but upon swapping out my older '00 stock alloy rims with new firestones, yep still he same damn sound. Nothing changes whether or not Im turning to the left/right. I took the lincoln around a few on/off ramps at 30-45 and the sound is the same whether or not Im driving straight or turning. Also, the car has no vibrations and drives straight as an arrow.