Blair's chapter on mufflers and the mathematics in it (the math in the book is available in a software program from SAE) is very useful if you are at all interested in the future of motor sports in general and track public relations, the general public's opinion of hot rod cars. I know some people would rather be loud than fast, but there is no good reason to be loud, and this is particularly so when it is possible to use the sound energy to increase the power output instead of aggravate people. He explains how the mufflers can be band-pass filters and how to use acoustics to cancel the peaks of select frequencies which a particular engine emits. Sound energy lost out the tailpipe is energy that could be used in the engine for something useful. Within Blair's work is solutions to design of systems, intake and exhaust, which utilize the acoustic energy and gas dynamics to improve engine efficiency. For instance, the speed of sound, hence the reflected wave, is different in CO2, CO, H2O, etc, and in a running engine all those exist in varying quantities in (what we usually think of as merely) air flow, when in fact it is not simply air, it is a varying mixture of gasses, each with significantly different characteristics
