I own a Tetratec Deep Water 96 that is realtively quiet. All you can hear is a slight hum from it. Now, I know that I have my Deep Water on a pillow, but that is because when I bought it I bought it used off of ebay and the guy who had it before me had broken it and fixed it in such a way that it made a lot of racket. That's probably why he sold it. Anyway, I had to turn every which way (on its sides, up-side down, you name it) to quiet it. Then I talked to my dad and he fixed what the previous owner did wrong and now it's very quiet. I also have a Rena 100 air pump that is quiet too. Both these pumps are hardly notoicable for me when it comes to noise, but the Deep Water is the most powerful of course and I'm sure if you get a good one that hasn't been tampered with like mine had yours would be quiet too. My dad's is and he got it used as well, but it hadn't had any problems like mine did.