could this be my tires???

Could be.. check pressure first off and if that doesn't work rotate...

I have driven countless B7's (cabrio, many sedans, a wagon) and I have noticed this in nearly everyone EXCEPT a brand spanking new loaner I once had (re: new tires). It seems to me to be much more pronounced when the warm weather arrives... almost "harmonic" rather than a real vibration caused by inbalance or a warped rotor.

One service tech swore I was crazy and was "trying" to hear it... It's one of the main reasons I got rid an '06 cabrio 3.0Q (along with an A/C system that couldnt keep a charge and was really loud as well). That car rode on Conti tires....

My current A4 (S-Line Sedan) has Dunlop tires which ride a little rough to begin with, (aggressive tread pattern) and I don't feel or hear it. My wife's car ('06 A4 Avant S-Line) has Conti's on it, and I felt it the other day for the first time in a long time (warmer weather arriving here in NJ).

Been having a lot of problems with my car....one thing in particular is this noise coming from passanger side....above 50mph or so....humming, high pitch...as if from the tires.
My car has been at 3 different dealers 7 or 8 times over the past 6 months....over 20 days total in thier shops.
Not sure how bad is yours but mine is really pronounced....I can hear it over radio but never with open windows...the wind and road noise covers it up completely.

Audi engineer came out a few times....wheel bearings, calipers, tires, wheels, drive shaft.
At this point I am fed up and ready to swear NEVER to buy Audi again.
PS: I am also in NJ