A few quick things to try: (1) put the air pump on something soft to absorb some of the vibration that may be causing the noise, (2) make sure the air pump is on a flat surface, (3) make sure the air line and air stone are clean and clear in order to reduce some of the back pressure, and (4) check the diaphrams inside the air pump to make sure there is no tears in the rubber and that there is a good seal. Good luck!