Just to stir things up...     It seems that with exhaust systems, the exhaust consists of two parts which should be handled differently.    Part 1 is the exhaust gas flow which we want to flow out with little restriction.   Part 2 is the exhaust pulse which we try to attenuate, breakup, etc.     These two are like the difference between wind and sound-waves.      In the past 24 hours or so, I've been wondering about using anechoic chamber principles to attenuate the pulse.      I have a specific layout in mind which should tend to attenuate the pulses while not interfering with exhaust gas flow.     Anybody hear of such a thing?

Tom (looking for project sponsors or a job)