An Investigation of the Adjustable Element Concept for Design of Automotive Exhaust Mufflers

The feasibility of employing a muffler with adjustable internal elements as an aid for design of production automotive exhaust mufflers is investigated. Design and internal geometry of the muffler are described and illustrated. Equipment and methods for measuring the acoustic reflection and transmission characteristics of the muffler for various adjustments and pure tone frequencies are presented. Results are analyzed and compared with performance data obtained when the source of sound is simulated engine exhaust noise. The value of the adjustable element concept for design of automotive mufflers, and the relative merits of pure tone and exhaust spectrum analyses, are discussed.