I purchased this air pump seeking a pump that would be able to power a large set of airstones at a depth of 3 feet. Many other pumps that I tried were not quite up to the task.
This pump is louder than a standard vibrator pump, but if you need a heavy duty device that pumps a lot of air, then this is the one.
Update: 8/18/2012 - I'm sorry to report that the pump has failed after 8 months of service at a depth of 3 feet. Although the pump was loud, it was acceptable given the volume of air that it pumped when new. However, over time it got louder and then lost the ability to provide even a meager amount of air at a depth of 3 feet.