Broadband and low frequency sound absorption by Sonic black holes with Micro-perforated boundaries

• Published in: Journal of sound and vibration Vol. 512; p. 116401
• Main Authors: Zhang, Xiaoqi, Cheng, Li
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 10-11-2021; Elsevier Science Ltd
• Subjects: Absorption; Acoustic black hole; Acoustics; Black holes; Broadband; Control equipment; Energy dissipation; Finite element analysis; Frequencies; Low frequency and ultra-broadband perfect sound absorption; Micro-perforated panels; Noise control; Sonic black hole; Sound; Sound transmission; Sound waves; Trapping; Wave retarding and trapping; Acoustic black hole; Micro-perforated panels; Wave retarding and trapping; Low frequency and ultra-broadband perfect sound absorption; Sonic black hole
• ISSN: 0022-460X; 1095-8568
• DOI: 10.1016/j.jsv.2021.116401

Acoustic black holes (ABHs) have been so far investigated mainly for flexural wave manipulation in structures. Exploration of ABHs for sound wave manipulation, referred to as Sonic black holes (SBHs), as well as the design of SBH-based noise control devices are scarce. To fill the gap, this paper proposes a SBH sound absorber inside a circular duct in conjunction with the use of Micro-perforated panels (MPPs) to achieve broadband and low-frequency sound absorption. Capitalizing on the ABH-specific wave retarding and trapping phenomena and the energy dissipation ability of the MPP, a compact and ultra-broadband near perfect sound absorbing device with sub-wavelength thickness is realized for noise abatement in a duct. Finite element simulations are performed to assess the achieved sound absorption performance, which is experimentally confirmed by impedance tube tests. Analyses reveal that the physical mechanism underpinning the superior sound absorption is attributed to the combined effects of the ABH-induced wave speed changes, energy trapping and the spatially graded local resonances of the cavity-backed MPP. The proposed solution shows promise for circumventing some existing limitations of traditional noise control devices.