well theres not much to explain, if u you look at a chambered muffler u can see how it deadends the sound and how it can create lots more resonence and even in a straight thru design. Theres soundeading material(fiberglass?) in the mufflers around the pipe... but the straight thru bullets are more like resonators then a muffler, as you can see theres not much it has to muffle with
ALl i know is there suppose to be the loudest style of mufflers. magnaflow magnapacks are another example of this