 It's the wheel bearings...............
In my case the hIgh-pitched sound became progressively worst, sharper. And yes, it would also go away in wet weather or after a car wash, but it would always return. The hsound became so bad that I could barely drive the car. I brought it to my Ford dealer. I showed the Service people a TSB on the 2005 Ford Freestar and the defective bearings. They would do nothing unless "they (Ford) heard the sound". Also the service people claimed there was no service bulletin for the bearings, this dispite the TSB which they discounted as "being on the Internet" and thus of no value.
Finally, in a road test, a Ford mechanic "heard the sound" and knew almost immediately it was the front wheel bearings. I made an appointment for a few days ahead to have them checked, and I left the dealership.........I couldn't wait that long...........the next day the sound was so sharp, so painful, that I couldn't drive the car any more. I brought it to the service department, with a throbbing heahache and tears in my eys from the pain........the ladyin Serivce took my keys....the bearings were replaced that night.
I looked at the mechanic's report when I picked up the car the next day: the bearings were completely "finished", worn out.........at 62,000 kilometers!
IT'S THE BEARINGS...NOT THE BRAKES!!!!!!!!!!!!! | 
