I chopped open the muffler on my Corolla. I made a short video explaining how it works:
Here’s a few photos of the process:

























How it all works inside:





Sound travels as a wave in the exhaust stream, with a wave length of lambda:

In the perfect world, all waves would destructively interfere:







I was surprised that this muffler has a passive spring loaded door:

 

Nice work! Subscribed.

 

Good stuff, that's not stainless steel.