Mine was Loud when I first hooked it up. I was using a big Aqueon pump for my return before the sicce. The aqueon was quiet but high wattage. Like Big_Pun said, the energy consumption matters. I switched to the sicce and my temp dropped two degrees. Loud or not, I kept the sicce.

tg8gxp assured me it would get quiet after a few days. I suppose it did, but it was still louder than my Aqueon, not quite as loud as a Mag though. When it was still bugging me, we got some shower liner at home depot and made some little mats to absorb the vibration. Mine's not external though.

Are you hearing the pump/motor itself, or vibration? I've read about people using an old mouse pad under external pumps to help with noise. (That's why I tried the shower liner - made a big enough difference to be worth the trouble.)