Optimizing Absorption Coefficients: A Study on Acoustic Characteristics of Saturated Fluid in Porous Media

This study introduces an experimental approach for quantifying audible acoustic frequency parameters within a rigid porous medium using an impedance tube. Employing the equivalent fluid model, a derivative of Biot's theory, we explore wave propagation intricacies within porous materials, emphasizing the pivotal roles of the effective density and dynamic compressibility of the saturated fluid. Our primary focus is on resolving the inverse problem, seeking to minimize both experimental and theoretical absorption coefficient expressions across the audible frequency range. Simultaneously, we identify and determine four critical parameters: viscous and thermal permeability, the inertia factor introduced by Norris, and the thermal tortuosity introduced by Lafarge. The research results encompass a thorough comparative analysis involving experimental and simulated absorption coefficients. This examination utilizes optimized parameters and spans across four diverse polyurethane foam samples. Through this comprehensive investigation, we elucidate the nuanced interplay between experimental observations and theoretical predictions. The findings not only advance our understanding of the intricate acoustic characteristics of rigid porous media but also contribute valuable insights into optimizing absorption coefficients and the broader field of wave propagation within such materials. This work stands at the intersection of experimental acoustics, porous media physics, and inverse problem-solving, providing a nuanced exploration of audible frequency phenomena.