A Bench Test Facility for Engine Muffler Evaluation 630283

The problem associated with laboratory evaluation of muffler acoustical characteristics are complicated both by the acoustical considerations involved in obtaining an adequate noise source and by the ambiguities involved in defining what constitutes quality in a muffler built for general application. In order to quantitatively define the characteristics of quality mufflers, an extensive series of field tests were conducted on a variety of sizes and types of mufflers in conjunction with four engine configurations. Work then turned to the development of a wide band siren noise source and acoustical test system which would simulate the high impedance character of an engine exhaust noise source, and in addition generate the necessary intensity and spectral characteristics required to obtain test data over the range of noise conditions encountered in the field. Weighted acoustical evaluation techniques were evolved for use with the bench facility to compare muffler quality over a range of exhaust sizes from 1–1/2 to 4 in. Based upon the results of these programs, a prototype bench test facility has now been built which should prove valuable both as a muffler test and qualification device, and research and development device for muffler and exhaust system design.