Speaker
Description
Porous materials are widely used for sound absorption, yet their acoustic performance can be significantly altered by the presence of liquid water. The effect of overall moisture content on the acoustic properties of porous and granular media has already been investigated, almost through experimental approaches. However, the spatial distribution of water introduced by capillary rise altering the acoustic properties of porous materials remains comparatively unexplored. This work is a first attempt to quantitatively explain how capillary-driven partial water saturation modifies the acoustic properties of a porous material with straight cylindrical pores. The porous structure considered here is fabricated using additive manufacturing and characterized by X-ray tomography and contact-angle measurements. The acoustic transmission and reflection properties of samples with pore diameters from 0.5 mm to 1 mm are measured in an impedance tube for several values of water content in a frequency range from 500 Hz to 3 kHz. The results highlight that capillary rise creates a heterogeneous wetted sublayer that reduces the acoustically active thickness and modifies the acoustic response in a frequency-dependent manner. These findings suggest that the spatial distribution of capillary water, rather than total water content alone, governs the acoustic response of partially saturated porous media.