Hi Marshall,
Do you have the RS package? Next time I get into my car (it has the RS, and it is an auto 2LT w/ sunroof) I'll try this and listen for the noise... but I haven't noticed it in the entire time that I've had my car. I have @ 3,500 miles on it already. Maybe I'm just never driving 16-17mph though?
In your case, does the sound disappear at lower and higher speeds?