T. Bravo and C. Maury
24th International Congress on Acoustics
Del 24 al 28 de octubre de 2022, Gyeongju, South Korea
Including sustainable materials in the design of sound absorbing extended wall-treatments for room acoustics often calls for in-situ experimental characterization of their acoustical properties. This experimental study shows how the impedance and normal absorption properties of anisotropic bio-based materials can be characterized from free-field collocated pressure-velocity measurements over a wide frequency-range. These properties are examined for a number of anisotropic fibrous materials with increasing diameter of their fibers, such as standard low and high resistivity fiberglass, goose down and sisal. They are assessed against a model for absorption in anisotropic bulk-reacting liners with variable fibers diameter and orientation. Practically, these materials are shielded from the room volume by perforated panels, that make them resonating absorbers in the medium frequency range. The effect of such porous shielding on their absorption properties is experimentally characterized by the free-field pressure-velocity technique. Comparisons against the model, that assumes a rigid porous shielding, revealed the beneficial effect on absorption of the panel volumetric mode induced by finite-size effects of the partition.
