Exploring acoustic wave transmission in micropolar plate in air

This study explores the behavior of sound wave propagation across a micropolar plate at diverse incident angles, specifically crafted from expanded polystyrene. Through a blend of theoretical formulations and practical experimentation, we scrutinize the alterations in transmission coefficients within the frequency spectrum, shedding light on the dynamic shifts in various vibrational modes. Utilizing a comprehensive setup comprising a loudspeaker, microphone, and National Instruments acquisition system, we meticulously discerned the initial trio of longitudinal vibration modes across a broad frequency span extending up to 70 kHz. Notably, despite the plate's inherent dispersion and attenuation traits, this experimental setup proved effective. A distinctive facet of our approach lies in the deliberate incorporation of multiple incident angles, which yielded crucial insights. Notable is the identification, within the experiments, of a critical angle, marking a transitional zone. Below this threshold, distinct Lamb modes dominate, while beyond it, the emergence of micropolar modes becomes apparent. These empirically validated findings, in alignment with theoretical projections, substantially enrich our comprehension of these materials' engineering applications.