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Description
In practice, the sound absorption of finite objects at grazing incidence is dominated by strong edge diffraction and non-local reaction. This paper proposes a 1D-microphone array method to separate incident, specularly reflected, and diffracted waves using the recently introduced boostlet transform. The method is inspired by classical ideas of separation via time-windowing and extended to a convenient approach with space-time-windowing. As long as the waves are spatio-temporally resolved (e.g., Rayleigh criterion), the separation of each wave amounts to thresholding a cross-correlation of boostlet coefficients. The sound absorption (with and without edge-diffraction) can then be calculated from the signal-energy ratio between the separated waves. The method is tested with a 1D microphone grid scanned with a movable microphone, a highly directive panel sound source oriented at grazing angles of 8° and 30°, and two sample materials: a bioboard and a rigid surface. The method currently requires manual tuning for each array configuration, and further work is underway to automate as many steps as possible. Ongoing efforts focus on applying these ideas to scattering coefficients and parametric studies across multiple sample sizes.