Sound insulation characteristics of a layered structure using perforated honeycomb panel

A honeycomb panel is used in various fields as structure materials and has high potential as acoustics materials. This paper demonstrates the unique sound insulation characteristics of layered structures using flexible sheets and perforated honeycomb panel (PHP). These layered structures are theoretically modeled as a three-mass system composed of PHPs, sheets, resonator's neck masses and multiple air stiffnesses. First, it is found that a peak and a dip arise due to resonance of the resonator and resonance transmission of the double-wall, even if the structure has little air-layer between PHP and sheet. Next, normal- and random-incidence transmission loss are calculated with changing several parameters. Then, it is found that the frequencies of the two resonances (resonator and double-wall) get closer, the dip of the resonance transmission become weak. Finally, the validity of the proposed theoretical model is confirmed by the measurement in the reverberation room. Furthermore, the effective installation method is suggested by comparing the difference according to the fixing method of the layered structure.