Active control of sound transmission through a honeycomb panel with feedforward and feedback control

This paper deals with the active control of sound transmission through a rectangular honeycomb panel. The authors have proposed an effective control method using point force actuators and PVDF film sensors to suppress the transmitted sound power through a thin flexible panel in a low-frequency range before. With the proposed method, the frequency range in which the control effect can be obtained depends on the natural frequency of the panel since the method can control the lowest three odd/odd structural modes. Therefore, in order to make the control frequency range higher, a honeycomb panel, which has high strength-to-weight ratio, is used as a target panel in this study. However, when the honeycomb panel is used, the characteristics of sound transmission are totally changed and then the control effect decreases around even/odd, odd/even and even/even mode frequencies. Hence, in this study, active control method comprising both feedforward and feedback control is investigated theoretically and experimentally. The direct velocity feedback control is added to the previously proposed SISO feedforward control system in order to suppress resonances of the even order vibration modes. The results show that the feedback control can improve the control effect around even order structural mode frequencies and that the proposed control method using a honeycomb panel is capable of proceeding the significant control effect for improving the sound insulation property over a wide frequency range.