Development of Transmission Loss Bench for Mufflers Based on the Transfer Matrix Method

Acoustic components are used in automotive exhaust systems to minimize the noise from the engine and, consequently, to offer more comfort and sound quality to the consumer. Thus, analytical, experimental and numerical studies of these acoustic filters become important in engineering. In this regard, the aim of this article is to report the development of an experimental bench for acoustic transmission loss based on the transfer matrix method for application in studies of automotive mufflers and resonators. The validation of the method was performed by comparing the results obtained experimentally to predictions of numerical simulations and analytical calculations carried out in an acoustic expansion chamber and in a Helmholtz resonator. After the validation, experiments with different automotive mufflers having diverse internal configurations were carried out in order to study the different attenuation frequencies of the components. The studies showed a suitable correlation between the experimental, analytical and numerical methods. The analysis of the acoustic components was concentrated on the characteristic noise frequency of an automotive engine, and the results showed a correlation between the methods, which was coherent for this specific range. Therefore, it was possible to analyze and study the different types of mufflers and to determine important project variables, which influence the level of the attenuation of the components directly.