Quote Originally Posted by mecheng View Post
It's on demand. Flip a switch to go from quiet to not quiet. It energizes/de-energizes a solenoid valve in the exhaust plumbing thereby routing the exhaust gases through a more or less muffled pathway.
Nice, I was expecting some kind of automatic solution but in all honesty a flip of the switch sounds better for anyone who would be in the market for this (enthusiast)