Dunno exactly, but I can tell a related experience.
My Lifan 150 with 32mm exhaust, 43mm short muffler, and jetting on the rich side, was super loud. Too loud for my liking. Way too loud for a friend with a nice farm. Really deep sound which traveled long distances. Some might like that. I hated it. Gave me a headache. So I fitted a YZ250 2stroke muffler which has a 28mm entry and a 26mm exit, and a can which is about 50mm longer. Well packed (not too much or little packing) and it is much quieter. Maybe a tad less grunt, but barely noticeable to me. Throttle response is still great. I got it used for $50 and a welder fitted it for me for $35. Real happy. It still is loud at times, but the real deep sounds are mostly gone. Also much quieter at low throttle opening. So now I can ride in places where previously I could not.