They should squeel like little girls on a rollercoaster when you are rolling backwards and you gently apply the brakes.
Yep, like Alex said going backwards, they will most likely squeel pretty bad, sometimes the first time you drive it forwards in a bit it will squeel, also randomly LOL. If it rains, they will sound like you put sand paper in place of brake pads because of the rust that has gathered... Its normal for big brakes. with hi performance brakes you either get lots of noise, or lots of dust. or sometimes both .