EasyPro has been making some waves of late with a new sound-dampening technology that's actually a component on the aerator pump itself.  This is a new approach because historically, most companies worked on quieting the output via their cabinets.  Sound-damping foam being the main approach. 

I finally got around to testing this new pump and am happy to say it is indeed quieter than the original SRC Stratus pump.  You can watch the video below to learn more.

In terms of a few details.  The original SRC 1/4 HP pump produced 63.5 db at 2', 62 db at 10', and 57.5 db at around 20'.  The new SRC 1/4 HP pump with Sound Shield installed came in at 58.5 db at 2', 55 db at 5', and 50 db at 10'!  It was notably quieter to the ear too with a more pleasing sound overall.