i've had a few rios and could not hear them. i'm not an advocate for those pumps, and prefer "quiet one" pumps over these, but try taking it apart and make sure the shaft is seated correctly. there is a little plastic thing that sits on the end of the shaft. if that's not in properly, they make an awful racket. the second option has been mentioned...some sort of rubber between the pump and the tank. i use a rubber mouse pad.