I have a 2008 TL Nav/AT with 115,000 miles (The only part replaces in the engine compartment has been the serpentine belt about 6 months ago). The vehicle makes a whining noise that grows louder and higher pitched as I rev the engine up. The noise is similar to what you hear from a dentist's drill. This happens when I am driving and while in neutral. If the radio is on AUX with no input it pics up on it and amplifies the noise.

I suspect either the water pump or the alternator.

Video/Sound:
Video/Sound with the radio on:

 

The A/C was off for both of the veideos

 

It could also be a ground from your radio