Analysis and Desigh of Mufflers — An Overview of Research at the Indian Institute of Science

The reciprocating motion of the piston(s) of engines and compressors and the associated intake and discharge of gases are responsible for noise radiation to the atmosphere that ranks as a major pollutant of the urban environment. Mufflers have been developed over the last seventy years based on electro–acoustic analogies and experimental trial and error. Passive mufflers based on impedance mismatch, called reflective or reactive mufflers, have been most common in the automobile industry. Mufflers based on the principle of conversion of acoustic energy into heat by means of highly porous fibrous linings, called dissipative mufflers or silencers, are generally used in heating, ventilation and air-conditioning systems. The author has been working in this area for over 27 years. Of late, he has been researching in the vibro–acoustics of hoses used in automotive climate control systems. The present paper gives an overview of the research findings of the author and his students in different aspects of active as well as passive mufflers in the last decade. The same are related to the contemporary state of the art. Finally, areas needing further research are indicated. \u