I'd like to see those Kevlar extensions! Nice explanation by them, by the way.
Nope. It is possible to design an exhaust that both flows freely and is quieter, by using acoustics rather than restriction. Loud pipes sell, unfortunately, because the rider's impression is that it is more powerful I suppose...
I don't follow the logic that if 450s are loud, no one should complain about me?
I'm not sure where you ride, but in a few of our common spots, there are usually a lot of riders around. By far, the newer 450 bikes are the loudest. It's just part of their design. When you combine a large bore, a short stroke, and a very high compression ratio, you end up with a very quick, short explosion that produces a very high amount of energy (more energy = more sound).
I have to disagree with you about the acoustics thing as well. When traveling, sound waves have the same characteristics as the exhaust gases themselves. The sound waves expand as they travel through the pipe, bouncing of the metal until they can exit.
The only way to cancel the sound is to design the pipe so that the sound waves bounce off the walls and directly into one another. The colliding sound waves break each other up a bit, resulting in slightly less volume.
The problem is, you are causing the sound waves to do something other than exit the bike. The exhaust gases follow the same path as the sound waves, so they too, are forced to do something other than exit the bike.
If noise cancelation technology was as good as what they say, we wouldn't need to buy ear-plugs at almost any pro-race, motorcycles or other vehicles.