Nokian i3 185/65/15 making noise

I own a 2007 Prius which purchased exactly one month ago. Currently I have 3000 kms on the car. I decided to trade my Integrity tires for the Nokian i3's last week. I can hear a humming noise from the tires at about 60 km/h, the noise continues to get louder until I hit around 90 kms/hr and then the noise level drops. I took the car in again today for them to check the balance. Two of the tires were slightly unbalanced, but they fixed the problem. I also took the cat in last night to a Toyota dealership to get a 4 wheel alignnmet. I can't stand tires that are loud. If the tires are making this much noise now what will they be like in 10 to 20 K. Has anybody else had this problem with these tires? At this point I can get Nokian to send another set to try, or go for another tire.

Thanks,

Farshad