Hello; Read the excerpt about the study. What i notice is a lack of any consideration for the facts that loud exhaust can increase performance. I do get that just having loud pipes may not actually increase performance since most of us cannot do expensive dyno sessions if we add aftermarket pipes. But the fact remains race car teams can and do that very thing and do find performance. So we mere mortals generally have to order from catalogues and hope the extra noise does include some extra performance.
Might I add that along with performance can come efficiency. My take is a tuned exhaust with low restriction can improve MPG's. Depends on how we run it.
But i knew a fellow who was so screwy he had to be careful if he ever did a 360 turn around lest he drill into the ground. Had to have straight pipes on his 1200 Harley Sportster. Funny thing was he wore earplugs when he rode. Claimed the wind noise bothered him too much. But an exception maybe.
Guess i am not a psycho after all. I like some noise but not the loud droning of some cars.