What is the most quiet return pump?

[craigwmiller]

I have 3 of the 2640 SpeedWave's in my sump (return + closed loop + utility), and they are silent on full power. I can hear the bubbles from the skimmer over the 3 pumps together.

One of the most important things with pump noises to ensure is that their vibrations are isolated from your plumbing.... It's amazing how a small vibration can be magnified and be very loud if it resonates through your entire return plumbing. Flex tubing right from the pump (if even just for a foot or so) will help noise from any pump immensely!