There may be some noise, but it shouldn't be loud. What kind of pads did you install?
Are you sure you didn't bend the splash guards (thin sheet metal) and they are rubbing on the rotors? If that were the case, you'd hear it when spinning the wheel, though.
All you can do is go try to bed the pads in and see if it quiets down. If not, then time to investigate. Brakes are pretty simple, if you did something wrong, it should be easy to spot.
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