Howdy Rob! Yes, I sort of lurk in the shadows sometimes. This is what happens when you don't have a Supercar, and you're visiting a Supercar website. I troll around in the "Other Muscle" section.
Here's some info on the tests. If you get a chance, look through Mr. Hand's book at a Border's or Barnes & Noble, and there's a whole chapter on exhaust system/muffler tests.
http://www.boyleworks.com/ta400/psp/exhaust.html