I'd imagine the noise if room it vibrating against the floor, wall or furniture. Before going out to buy a new one, do you have a small box you can put it in, to muffle the vibration.
Don't know if you have these brands across the pond, but Rena and Whisper I've hear are quiet.
75g Planted Barbs Denison, BlackRuby, Tiger, Albino Tiger, Green Tiger, Cherry, Gold, Checkered, Odessa.
NonBarbs Cardinal, Neon, RummyNose, Bloodfin Tetras, Z. Danios. 1RTS. Amano, Bamboo, Ghost & RCS. 20g Long Shrimp Tank RCS, Tiger, Amano.