'06 RL Whining Noise

Anybody heard of this problem? Our '06 RL started making a high-
pitched whining noise that kicks in at a certain speed (varies, but
mostly around 40-45 mph), increases in pitch as the speed increases,
then diminishes in pitch as speed falls off, stops when speed goes
below original speed when it started. Hit the same speed, and it
kicks in again.

The dealer's had the car on five separate occasions for upwards of 20
days at a time, and they're nowhere near figuring it out. One of
their mechanics was convinced it was wind noise coming through the
windshield, and over my outright objections, sub-contracted the
windshield for replacement. NOW we have a wind noise in addition to
the original whine.

The latest news from the dealer is that they're working with the Acura
tech group out in Torrance, CA, but no solution as yet. We're growing
increasingly impatient - we've had various loaners - TL's, RDX's,
MDX's - but sorely miss our beautiful RL. Any observations, comments?

Thanks, Joe in Norwalk, CT