What he had was pretty basic. He had an extreme problem of a tiny room(8" x 10’) and a giant shop vac with one or two people changing out the buttons to several computer-controlled lathes.
The exit was on the bottom like a small rat maze, not wanting to inhibit the flow of air but enough sharp turns that the sound could not follow. The shop vac had its own tornado built-in as how it worked with the bottom like a 40 gal. drum and 4" PVC pipe going out and around the room and the pipe sealed where it entered the box. He used 3/4 in plywood and thinking about it, the foam alone would go back and forth like a speaker for the amount of give that it had, and the 3/4 plywood had none. I would run the design as you would for the Glowforge and just order the plywood at that size. and be sure to have a soft seal at the door to stop the sound from coming out that way.
The brush-like small enclosure at the business end would seem to be the expectation and likely sold by the company making the machine so it would be made to work with that machine. As the material for the contact lenses was light just an open 3" pipe was enough to gather the shavings the lathe produced as they happened.