If the car makes this sound frequently the best advice that I can give you is take the car to the dealer, and ask one of the techs to go for a ride with you in your car so that they can hear the sound itself. The best places to hear the noise is side streets when you drive next to parked cars, or bridges with raised walls/medians the sound will reflect off of the wall/car and will be much easier to hear.

When I had my 06 it made a sound very similar to this and took 5 or maybe more trips to the dealer in order to fix it, every time the sound would go away and then come back. sometimes the same day, sometimes a week later. they changed the brakes multiple times (or so they said that they did) they ended up changing the entire rear axle, and swapping it with a new one and that finally fixed it. Somehow my axle got bent slightly, just enough to make an irritating noise, semi-high pitched, metal on metal sound, and only when the car is moving. Probably from potholes or speedbumps (terrible roads here) Took about a year and a half, for them to finally eliminate the noise from my first trip to the dealership.

 

I'll definitely tell them about the axle. Mine is getting slightly louder to where I can here it with the windows up no problem if the radio is off at highway speed. They won't be able to deny it lol.

 

I took it to the dealer today. Luckily I think it was the Service Managers son who worked in the quick lube section that did a ride along. The service writer informed me that she sent off the request to Ford for a new axle but I have to wait until a weekday to drop it off because the Service Manager himself needs to also sign some paperwork etc. All in all, they diagnosed it as a bent axle defect and they admitted that there were no signs of racing, abuse, or accidents and it would definitely be covered. I was amazed that on a Saturday it only took them an hour to come to that conclusion and put forth the paperwork. Guess I'm one of the lucky ones depending on how you look at it lol.

 

Oh yeah, they even took off both rear wheels, inspected the brakes and suspension/bushings, rotated the tires, and re-test drove it.

 

I dropped the car off on Monday as they were closing. I get a call at about noon on Wednesday saying it's done! Pretty fast turn around. They replaced the axle and seal/bearing etc. No more noise! I'm stoked!