The reduction of noise is the result of several things.
The overall length of the exhaust run is increased from going up into the sep and then coming back down. Longer run makes the noise further away
The noise path is more torturous, 90* turn up, energy to push the water uphill, 180* at the sep, another 90* at the bottom, the more torturous the path the more noise energy is reduced
The sep itself is designed with a baffle to reduce noise
All these features PLUS the elimination of the splashing contribute to the reduction of exhaust noise.
Originally Posted by Miss Rachel
The exhaust is quiet. Real quiet. Not sure how it manages to suppress the sound so much but I surmise the exhaust pulses are pretty much eliminated after passing through the NL muffler and then the Gen Sep box.