enzo d
Check out the Silent Air range. Their pumps are really quite. :)

Hon3y_Bun
tetra whisper air pump. about 10 dollars at petsmart, and worth the bucks. It's soundless.

Adam T
cover the pump in in a old bit of clothing i do now i cant hear it

Roberto G
Most Tetra Whisper airpumps are pretty quiet. Your airpump may have a broken flap valve or diaphragm which causes it to be noisy. Have it checked in your local fish store. You can also get replacement parts from them.