Lets be sure the GFCI box is tight too as some are bolted and some are riveted to the Quiet Air cabinet. If you have the plastic intake filter on the pump with the foam filter you need the upgrade to the metal muffler with paper air filter.This change lowered the decible level about 25%If you already have the black metal muffler lets be sure the paper filter is inside. The outside of the canister will turm about 1/4 inch to unlock. If you do not have the new design have your dealer send you one as if this was recently bought there wont be a charge for it.Let me know. PS I always use a 1/16 piece of belting to cushion the back of the cabinet from vibration noise on whatever I am mounting the cabinet on. I stood 50 ft away from both of my Air1 display models running this evening and could not hear them run.(yes I may need a hearing check) \:\) Let me know, Ted