I had one for a fw tank once, and it was quieter than an old challenger air pump i had. the little giant was in my bedroom, no cabinet, and i managed to sleep so i consider it relatively silent
I have always used the 3mdqxsc pumps and they are relativly quiet. Under a stand I can't hear mine over the overflow at all. A buddy of mine has the 4mdqxsc and it is noisy because of the fan on the pump. The 3md does not have a fan on the pump.
As a side note, I just set up my Ampmasters on my new system and they are amazingly quiet. More quiet than my Little giant by far. Also the motor housing stays so much cooler than my Little giant pumps. They get very hot. They are reliable though and I have had them for many years.
