A consideration for attenuation of expanded silencer

Abstract

An expanded silencer is well known in all other silencers and widely used in an industry field. As the theory of the expanded silencer has already been established and it is considered to be useful because it has good visibilities of the silencing effect. In general, the performance of silencers is evaluated by the silencing effect(ATT) and insertion loss(IL). When we calculated the silencing effect by using the transfer matrix method, we experienced that the inlet tube length was completely independent of the silencing effect. Is the fact true? It is the motivation of this investigation. There are many studies on the characteristics of the expanded silencer. However, the effects of the inlet and outlet tubes on the silencing effect are different from each other and inconsistent. In this paper, it will be discussed the results of ancestors to find out why there is no unity. As a result, it was clarified to be existed the derivation process of the equation of the silencing effects of ancestors.