You might just want to get a quiet air pump Amberleaf. I find the Rena pumps with the flow adjustment knob on them are quite quiet in operation with no particular measures being taken to try to quiet them down. I have one running 4 air stones on my 120 gallon that has been doing it for about 5 years and it is dead silent and still going strong after all that time. When I read that the Whisper air pumps, the funny looking ones with the arch shaped case, were quiet, I bought a couple off of E-bay and was very disappointed at the extreme noise that they made by comparison.