Experimental and numerical investigation of acoustic scattering using boostlets

Participating speaker: Augusto Fantinelli, Visiting PhD student, Ramon Llull University, Spain.

Abstract: Modelling the interaction of sound waves with objects and surfaces is challenging due to the complex space–time behaviour of acoustic fields. In practice, surface roughness and finite object dimensions cause sound reflections to deviate from ideal specular behaviour, producing scattered and diffracted fields. While separating the total sound field into incident, reflected, scattered, and diffracted components is conceptually appealing, achieving it from spatial measurements remains a non-trivial problem. This work applies boostlet decompositions to simultaneously separate and analyse these components using a 1D line microphone array near the scatterer. The core idea is that each wave results from geometrically thresholding boostlet decompositions. The method is applied to a benchmark problem in which a spherical wave impinges on a circular disk of radius 40 cm. Measurements are performed in an anechoic chamber using a 6-DOF robotic arm mounted on a linear track, sampling the acoustic pressure along the axis and in front of the disk. Numerical predictions are obtained using an edge-diffraction-based method that separates the time-domain solution into geometrical-acoustics and diffraction components. The reconstructed direct, specular, and edge-diffracted fields are validated against these components and compared with the experiment, and estimating a scattering coefficient is left for future work.