Speaker
Description
The search for sustainable alternatives to conventional porous absorbers has increased interest in bio-based materials for acoustic applications. This paper investigates the normal-incidence sound absorption performance of bonded oak-apple panels manufactured using two different processing strategies and compares their behavior with that of a commercial polyurethane foam of equal thickness. Measurements were carried out using an in-situ acoustic impedance method based on combined sound pressure and particle velocity sensing. To support the interpretation of the experimental results, an equivalent-fluid modeling approach based on the Johnson-Champoux-Allard formulation was adopted. An inverse parameter identification procedure was implemented to estimate effective macroscopic properties from the measured absorption spectra, including airflow resistivity, porosity, tortuosity, and equivalent viscous and thermalcharacteristic-length factors. The identified parameters are discussed as effective descriptors of a heterogeneous bio-based porous composite rather than intrinsic material constants. The results show that oak-apple panels provide competitive mid and high frequency absorption and confirm the potential of this naturally derived material for sustainable acoustic treatment solutions.