Acoustic modeling of silencers-practical and theoretical

Abstract

Consulta en la Biblioteca ETSI Industriales (7776)

[EN] The current project deals with the study of acoustic silencers. More concretely, those silencers whose conduits transversal dimensions are small compared to the wave length of the sound, which flows throughout them. The principal applications of these kinds of silencers are the exhaust pipes in vehicles and the conduits of ventilation, air conditioning and heating installations. In the first part of this work, silencers with constant circular section are theoretically studied with the development of different expressions and graphics, which allow us to understand how the sound waves flow and to obtain theoretical values of the insertion loss R. This study is carried out with a simple change of section, with a silencer formed by one chamber and by two chambers. The following step of the project is based on the analysis of silencers, named, silencers of variable longitudinal section. In this case, one of the longitudinal sections considered has a sinus variation and other one has a triangular variation. Theoretical expressions and graphics have been developed too. The last step is focused on an experimental silencer which is setup in the laboratory of the Institut für Technische Akustik in Technische Universität Berlin , with certain characteristics. The theoretical results of the behaviour of this silencer are compared with the experimental ones in order to observe the differences between them and to consider them in the real silencers design. The concept of active sound absorption has been taken into account in this practical part, since in the last pipe of this silencer the sound wave is theoretically supposed to be totally absorbed.