It may have to do with where the air pump is situated. The pump works at optimum level when it is above the water line, on a shelf above the tank for instance. To help with any noise issues due to vibrations, you could a strap a sponge to the underneath so it isn't directly touching the surface.

Make sure that the airline is secured well and that there are no blockages or items crushing the pipe. You should also inspect the outlet connection point for any damages or obstructions.

If you would like any additional troubleshooting advice, contact our customer services team who will be happy to advise you further.