Ive found theres not really such thing as what i would call a quiet air pump. If you just want it for the bubble and the visual effect get a small one and have it on a timer in the day. But otherwise if you have good filtration i wouldent bother
i do have really good filtration i have one tetratec fx 700 (external), and a jewel filter that came build in with my tank. its really just for decoration so theres something else going on in the tank..