On effect of inlet tube on attenuation of expanded silencer

• Published in: Kikai Gakkai ronbunshū = Transactions of the Japan Society of Mechanical Engineers Vol. 87; no. 895; p. 20-00385
• Main Authors: ISHIHARA, Kunihiko, KOBAYASHI, Kei
• Format: Journal Article
• Language: English; Japanese
• Published: The Japan Society of Mechanical Engineers 2021
• Subjects: Expanded silencer; Insertion loss; Radiation impedance; Silencing effect; Sound and Acoustics
• ISSN: 2187-9761; 2187-9761
• DOI: 10.1299/transjsme.20-00385

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 exceptional prospects. There are many studies on the characteristics of the expanded silencer. For example, Davis D.D. et al. constructed the theory under the assumption of no reflection of the tail pipe. Fukuda et al. have left a trail of many fruitful results on the characteristics of the expanded silencer including the effect of the tail pipe. 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 silencing effect was completely independent of the inlet tube length. Is the fact true? It is the motivation of this investigation. We noticed the silencing effect was different from the insertion loss in the process of this study. This is considered to be natural and almost all people know that fact. In this paper, it will be verified that the silencing effect is independent of the inlet tube length and we modified the silencer effect by taking into account of radiation effect from the outlet tube and compared the modified silencing effect and the insertion loss. As a result, it was clarified that the both results are good agreement with each other.