I've used them. They are fairly quiet. I think the one I bought at Wal-Mart was super quiet. I'm pretty sure it was an Aqua Culture. I just used it in my car to transport a fish. I had to touch it to make sure it was working.
My whisper 100 was great until it got real noisy after 6 months......Still works fine but i retired it.......I picked up the biggest Petco model with 4 outlets....running great so far!