What kind of filter is it? Canister or HOB
? If its a canist er you might need a tuneup (Impellar, Impellar shaft, Impellar cover, etc.). My fluval made a bunch of noise and it ended up the shaft cracked and was shaking around ultimately hindering the flow and effectiveness of the filter.
Bought a tuneup kit and it's practically silent now. I also have my filter positioned on top of a towel folded up to absorb the vibration a bit. Works great.