I believe the tire brand/model will determine road noise more than the actual size. If you find a tire that you might want to buy, check for reviews at
www.tirerack.com . In case you're not familiar with the site, go there and click "tires" at the top, then on the lower right click "browse by tire brand" and you can choose the brand and then the model. I currently have Bridgestone Potenza RE71 tires that make a little noise, but it's not too bad. I can hear a humming sound if I turn the radio down. I've also driven a car with Nitto NT450 tires, and I found them to be noisier than the Bridgestones.