A Pump Question

I just got my brand new 120 gal tank up and running. After running all the plumbing, I fired up the pump. Boy is this thing loud, I have insulated the stand with 1" styrofoam and built (well almost) a cabnet for the bottom and it is still loud. Is this normal? The sound of the pump running is louder than the water in the overflow. I hard piped it most of the way and used a 8" piece of flex PVC just before the pump. I am using it as the return pump and it is a vibrating type noise. The vibrating is comming from the pump and not from the piping. The pump is a cap (coolie Aqua Pump) 5000. Or if anyone has any idea's on how to quiten this thing up

I tried lifting the pump off the bottom of the tank using the suction cups provided to hang it on the side of the sump and the noise was the same.