At 5:02 is the spark arrestor. It is a restriction but it keeps any sparks from flying out and lighting dry grass or leaves on fire. The baffles on the main half is what kills the sound.
It also keeps mice from getting in and making a nest which is what they did to mine (happens all the time to people) and others who have one from a manufacturer who didn't have the foresight to use a grill or sieve type opening.
Informative video👍. Not too many people dare to take a mower muffler or 2cycle muff apart. Good post. I was looking for information on this. I'm thinking it's possible to service these if you can open them easily and hit em with a butane torch to burn old oil buildup. Or wrapping it in aluminum and throwing them in a BBQ coal pit ,like I've heard in mower blogs. If this muffler clogs on a mower or 2cycle it will not start or make it bog down
