Review on Efficient Aeration with Eheim Air Pump 400 by Matt Pratt

Not quiet, but quieter than many. Your silence threshold is relative. The pumped volume isn't excessive and is close to the dual-output whisper (1/3 the price and much louder) that it replaces. Compared to most air pumps made for aquariums since the 1960's, this air pump is one of the quietest and by far the most expensive type of vibrator I've owned for the volume pumped. The resulting noise can still be heard and can be reduced by placing it in a cupboard. If your bubbles are louder than the pump, you may have a "quiet" pump for your purposes. I have this pump as an air source for many tanks (9 - 2 1/2, 2 - 10, 1 - 55) and there are many air outlets, so in my case the bubbles are louder than the pump. For me there is no "extra" air to use - 14 outputs. Rating: 3-4 Pros: Quieter than many double sockets, each socket is controlled separately, has a hole for hanging on the wall, sufficiently long power cable, comes with hose and eheim adjustable air stones. The audio is around 48dB while most others have 70dB. Small size. 3 year guarantee. Cons: very expensive for such a volume of pumped air. Certainly not silent. for the same price, the Hygger is quieter and pumps a lot more air.