I used to get a slight humming sound from the pump as it would vibrate on the bottom glass , I added a cut up piece of filter media and placed it under the pump no more humming sound .
I used to get a gargling sound from the water kicked out of the pump as it always splashed above the surface especially when the water was low from evaporation .
I added a deflector on water outlet to keep water movement under the surface no more gargling sound , still get the same flow and performance just with out the noise ,
There are many simple fixes that can be done with basically anything around your fish tank . a little imagination and you can rig up just about anything