98 Taurus noise

I'm going to do my best to describe this. Hopefully someone will have a
good idea what I'm talking about.

I test drove a 98 taurus (105k miles) today. All was well, at first. About
7 minutes or so into the drive, at about 35-40 mph, I started hearing a
noise that sounded like it was coming from the rearend. like something was
rubbing, but not constantly. It wasn't a squeaky disc brake noise, it was
lower pitch than that. Kind of a woo-woo-woo-woo sounding noise. It would
stop when I tapped the brakes then start up again in less than a minute. It
seemed to get worse as the drive went on. The noise would start at lower
speeds. It still wouldnt be constant, but would get more frequent. The
performance of the car seemed unaffected, but the noise was loud enough to
be annoying.

The dealer said they would take it to their mechanic to have it checked.

I'm thinking it's a brake drum issue, but I'm no expert.

Any thoughts??

TIA!!!
^JR^