Low-Frequency and Large-Scale Hybrid Sound Absorption Using Active Force Control
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ORIGINAL PAPER
Low-Frequency and Large-Scale Hybrid Sound Absorption Using Active Force Control Yang Liu1,2 · Kean Chen1,2
· Yanni Zhang3 · Xiyue Ma1,2 · Lei Wang1,2
Received: 21 June 2020 / Accepted: 15 October 2020 © Australian Acoustical Society 2020
Abstract Effective low-frequency and large-scale noise reduction are crucial in industrial applications. Conventional passive methods lack the effective low-frequency performance, and existing hybrid methods are costly to realize large-scale absorption. Hence, an effective and simply actuated solution for low-frequency and large-scale absorption is urgently needed. In this study, the low-frequency (100–500 Hz) quasi-perfect absorption characteristics of a hybrid structure which adopts the active force control (AFC) strategy are confirmed by experiment and its large-scale properties are analyzed. By using a flexible plate driven by a concentrated force as the AFC component and a passive MPP absorber, the large-scale model is established to absorb the normally incident plane wave. The structural–acoustic coupling characteristics are analyzed in detail and validated both by the experiment and finite element method. It is observed that by the acoustic–structural coupling, the frequency shift of the first structural mode will be inversely proportional to the total depth of the air cavities. Key parameters relating to the control force and other specifications of the hybrid system are analyzed to improve the broadband performance of the hybrid structure. Owing to the optimized control force, the coupled structural modes could be used to realize commendable large-scale (up to ten times larger than conventional hybrid absorber) absorptions. Compared with conventional methods, the designed absorber is able to realize low-frequency broadband quasi-perfect absorptions while dramatically reducing the number of secondary sources. Keywords Vibro-acoustic coupling · Structural mode · Active control · Noise control · Vibrational acoustic radiation
1 Introduction Passive acoustic treatments like resonant absorbers, porous materials and flexible materials have been successfully used in noise reduction for decades. However, one single structure/material with a fixed specification merely works in a certain (sometimes narrow) frequency range [1, 2]. To overcome such weakness, many composite models were proposed. Typically, modified models based on the multiple layers [3], ameliorated resonant cavities [2, 4] and passive
B
Kean Chen [email protected]
1
School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, Shaanxi, China
2
Key Laboratory of Ocean Acoustics and Sensing, Northwestern Polytechnical University, Ministry of Industry and Information Technology, Xi’an 710072, Shaanxi, China
3
Institute of Launch Dynamics, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu, China
layer with modified specifications [5, 6] have been investigated. Furthermore, sub-cells with certain absorption bands were parallelly arranged to
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