These Active Aqua Air Pumps are super silent with a multi-level muffler. They have the ability to have the pressure adjusted freely with low power consumption, and are available in either a single or dual outlet and includes a one year warranty.
Nice little pump at a great price. I have two stones running off of each outlet and keep it on its highest setting at almost all times. it keeps both of my DWC buckets bubbling nicely with minimal noise.