Billa is right about not restricting the inlet. Found that one out the hard way
That Sedra 3500A that I got was noisy as hell and after trying to work with it for about 2 months I gave up and bought an Eheim 1250. That Sedra had almost a 1" inlet and a 3/4" outlet! Tried to reduce it to a 5/8" inlet and a 1/2" outlet; the pump turned into the noisiest part of my whole setup (could not even hear my Sunon 108cfm fan over it)
Eventually I might use that pump for an external water chiller some day but till then it is collecting dust and I am enjoying the silence of the Eheim.