Yep Rotary vane for sure from my experience. I have a 1/4 horse Gast rotary vane that you have to walk up on to hear. The other two rocking piston aerators I have one of my neighbors complained about the sound a couple of years ago. He's a good 250 feet away but he was too cheap to air condition his house when it got hot, and left all the windows open. Funny he didn't have a problem with all the semi's that go by on the highway.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.