I don’t know about that. I have an older sport quad ATV. Loud AF with custom exhaust the last owner installed. I have full control of the fuel delivery with the carb mixture/jetting/etc, and there is no nothing other than preventing backfiring/popping that has any effect on the noise. I even tried repacking the “muffler” with new stuffing—- didn’t help.
Most newer bikes barring maybe Harleys come stock with exhausts that aren't monstrously loud because of regulations (though some have ways around that).
Problem is most peoples first course of action is to modify it to sound louder/"better". You'll often see this as the first complaint people have about bikes in motorcycle review videos.
My current bike is a newer CBR650R, mand it sounds relatively tame. But some people complain about that.
An older vehicle I may not fault as much, but you also have people revving to redline for no probable reason.
