I've been on the search for a Airpump that is quiet and won't need me to place a towel or prop it up so that it stays quiet. After searching for a while I finally broke down and tried the Tetra air pump the whisper air pump is a great design I wish it was grey though to be able to hide it better when I have no stand on some of my tanks. With other air pumps I would have to unplug them when watching TV or going to bed because of that humming noise. So I tried placing a towel under that but thought that could be a fire hazard.
So if your tired of humming and buzzing try this Tetra Whisper air pump, it comes in many different sizes for all sorts of tanks and the larger models have more than one output for air. The price is another thing I love about this because it's cheap but works great.