The low noise is definately quieter which I believe is good because the delta barrel 4 is a loud pipe to begin with (some say). My butt dyno had trouble dialing in the differences as I still consider myself a newb to riding. Regardless, my wife, while driving behind me on the highway, did not feel like an attack helicopter was circling above. Which was her comment about my pipe with the "sawed-off" Restrictor I had in it when I bought the system (used). Anyways, a huge improvement and I highly recommend if you're looking to quiet your delta pipe.