Simultaneous inverse characterization of five non-acoustic parameters for rigid porous materials through normal surface acoustic impedance measurements in impedance tubes

Simultaneously characterizing five non-acoustic parameters of open porosity, flow resistivity, tortuosity, and viscous and thermal characteristic lengths is crucial for acoustic design of porous materials. While established methods are effective for absorbers with porosity larger than 0.95, specific technical challenges remain for rigid materials with intermediate porosity ranges. This paper presents an integrated inverse characterization method that combines the Wilson model with the Johnson-Champoux-Allard (JCA) model for simultaneous parameter determination in rigid porous materials. The methodology employs the two-microphone transfer function technique in impedance tubes compliant with ISO 10534–2, streamlining the characterization process without requiring additional specialized equipment or complex experimental setups. Parameter inversion is performed using the integrated Wilson-JCA framework for optimization robustness. An enhanced Sequential Quadratic Programming algorithm with a systematic grid search strategy determines the non-acoustic parameters within appropriate physical boundaries, effectively avoiding local minima and enhancing the robustness and reliability of the parameter inversion process. Experimental validation was conducted on four open-cell ceramics with porosities ranging from 0.84 to 0.92 using impedance tubes with cut-off frequencies of 1.6 kHz and 6.4 kHz, achieving absorption coefficient residuals below 0.04 and 0.05, respectively. Predicted acoustic impedance and normal incidence absorption coefficients demonstrate close agreement with experimental measurements and published data. Independent validation exhibits relative errors of less than 2 % for open porosity and 10 % for flow resistivity, confirming the method’s precision for intermediate-porosity materials. This integrated Wilson-JCA framework with enhanced optimization provides a reliable and efficient approach for material characterization and acoustic design optimization.