I manufacture AES mufflers. To make a good straight through (absorbtion) muffler you have to tick all the boxes. The perforated tube must have the correct open area ( holes /sq in. and between 3 and 3.5 mm) I wrap the perforated tube with INOX which is capable of high temps and then pack the muffler AT THE CORRECT DENSITY with either quality stranded fibreglass or GTB depending on the application. If it is a circuit racer then packed entirely with INOX. I also install an expansion joint in the perforated tube to prevent fatigue. This makes it possible , with some effort to repack the muffler if ever required giving it a second life. The biggest killer of mufflers is carbon resulting from a bad tune, too rich. These mufflers were developed on rotaries which provide the worst possible enviroment for a muffler i.e. very noisy and hot. They have a deeper , quieter sound. I am continueing r&d constantly to improve. It is all about silent high flow.
