Study on acoustic coupling by micro-perforated panel in asymmetric Helmholtz resonator

Abstract

In this study, the acoustic properties due to the acoustic coupling effect of the sound-absorbing structure composed of two Helmholtz resonators with different characteristics and a microporous panel were confirmed. The two resonators are designed with intrinsic acoustic characteristics distinctly distinguished in frequency domain even if when measured together, and the porous panel is inserted between the structures. The sound absorption coefficient, reflection coefficient, and acoustic impedance results of the proposed structure were obtained through eigenvalues of the transfer matrix that was calculated from the frequency response function measured using the impedance tube and the 4-microphone method. Through a case study, the contribution to effective factors such as the impedance of the resonator, the size and number of holes on the boundary surface was identified. The performance in the target frequency band was verified through the theoretical model of the sound absorption structure to which the above parameters were applied. An active control system that can control the sound-absorbing structure composed of an actuator and a perforated plate was established, and noise reduction effects were produced according to various noise environments.