BROADBAND SOUND ABSORPTION OF PERFORATED PANEL WITH TUBE BUNDLES BASED ON IMPEDANCE DECOUPLING

In the sound-absorbing structures based on resonance, acoustic resistance and acoustic reactance are usually coupled together, which affects impedance matching to obtain good absorption performance at required frequencies. To address this problem, a perforated panel structure with segmented impedance-decoupling tube bundles (PP-IDTB) is proposed to realize the decoupling of acoustic resistance and acoustic reactance. Theoretical and simulated results show that by changing the diameter of the upper thin tubes, the acoustic resistance can be varied, while the acoustic reactance remains constant, and thus the bandwidth of the absorption peak can be adjusted. The acoustic reactance varies with the length of the lower thick tube, while the acoustic resistance remains almost unchanged, and thus the resonance frequency of the absorption peak can be shifted. Moreover, impedance decoupling can improve the impedance matching effect in a wide frequency range, further enhancing the broadband sound absorption performance. Based on this, a parallel-coupled structure consisting of 9 PP-IDTB units is proposed. For demonstrating broadband absorption, the designed structure with a deep subwavelength thickness achieves near perfect absorption within a wide frequency range from 300 to 400 Hz. The design concept of impedance decoupling contributes to construct sound absorbers with highly efficient low-frequency broadband absorption.