title: Hybrid noise control in a duct using a light micro-perforated plate.
abstract: A plate silencer consists of an expansion chamber with two side-branch cavities covered by light but extremely stiff plates. It works effectively with a wide stopband from low-to-medium frequencies only if the plate is extremely stiff, to ensure a strong reflection of acoustic wave to the upstream in the duct. However, a plate with a slightly weak bending stiffness will result in non-uniform transmission loss (TL) spectra with narrowed stopband. In this study, a hybrid silencer is proposed by introducing micro-perforations into the plate to elicit the sound absorption in order to compensate for the deficiency in the passband caused by the insufficient sound reflection in a certain frequency range due to weaker plate stiffness. A theoretical model, capable of dealing with the strong coupling between the vibrating micro-perforated plate and sound fields inside the cavity and the duct, is developed. Through proper balancing between the sound absorption and reflection, the proposed hybrid silencer provides a more flattened and uniform TL and a widened stopband by more than 20% while relaxing the harsh requirement on the bending stiffness of the plate. Theoretical predictions are validated by experimental data, with phenomenon explained through numerical analyses.
authors.affiliation: Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong Special Administrative Region, China.
authors.forename: X N
authors.initials: XN
authors.lastname: Wang
authors.forename: Y S
authors.initials: YS
authors.lastname: Choy
authors.forename: L
authors.initials: L
authors.lastname: Cheng
mesh_terms: D000042:Absorption; D000162:Acoustics / Q000295:instrumentation*; D003198:Computer Simulation; D004548:Elasticity; D004738:Engineering / Q000295:instrumentation*; D004867:Equipment Design; D008962:Models, Theoretical; D009038:Motion; D009622:Noise / Q000517:prevention & control*; D009716:Numerical Analysis, Computer-Assisted; D016062:Porosity; D015203:Reproducibility of Results; D013997:Time Factors; D014732:Vibration