Development of acoustic “meta-liners” providing sub-wavelength absorption
Résumé
The sound absorptive performance of a proposed “meta-liner” are investigated in this paper. The structure is composed of closely placed plates connected by openings at alternating locations in a stacked format. This system presents multiple band gaps with high absorption and sub-wavelength behaviour (sample thickness equals 0.04 λ), achieved through tortuosity within the design. The acoustic response of the single layer is obtained numerically and with experimental verification under normal incidence. The repeating cellular design allows efficiencies in the viscothermal numerical analysis and using a transfer matrix approach, it is demonstrated that the response of the overall system may be efficiently predicted from a detailed model of a unit cell. Both the transfer matrix method and a full viscothermal model are validated against experimental data as a function of system depth. The analysis gives very satisfactory results which could form the basis for future designs.