I have been looking for a quiet air pump for long long time, until I found this. I want to share my experience on this quietest air pump I have ever used. I have been using this air pump for 6 months. very very very quiet, I cannot even hear it unless I put my ear beside it. The only problem is it might be not powerful enough to run in big aquarium, but still I am very satisfied with it.
This brand has 2 models, 1 output & 2 output versions. The 1 output version is on sale on amazon.ca now, and I bought another 3 this time.
Update: Amazon changed the on sale price, not very attractive now. was $13 when I first started this post.