I think this is a HOB where the powerhead is in the tank. You should take it apart and make sure the impeller is clear (not wrapped in moss or a piece of shipping cardboard). Also fill the tank to 1 finger's width below the rim. Make sure the blue plastic bumpy thing is in the waterfall the right direction.
I am at a loss then you may have bought a bad one. with any HOB filter there will be some splashing noise but it should be relatively quiet if you want perfect silence you will have to check out a canister filter or go all out with a wet/dry. Personally if you can take it back I would do so try a new one or try a whole new brand whatever your choice sounds lie you have a bad filter if it is making lots of noise. Also I had to put a book on top of an old HOB a long time ago to keep the top of the filter from rattling so bad.
55g#2- 2 discus, 1 angle, and a clown loach
30g- Black ghost knife
20g long-electric blue crayfish
10g-mystery dwarf cichlid