How diffraction limits ultrasonic screening in phononic plate composed of a periodic array of resonant slits |
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Affiliation: | 1. Institut FEMTO-ST, Université de Franche-Comté, CNRS, 15B avenue des Montboucons, 25030 Besançon cedex, France;2. Laboratoire de mécanique et d''acoustique, UPR CNRS 7051, 31, chemin Joseph-Aiguier, 13402 Marseille cedex 20, France |
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Abstract: | We explore experimentally the role played by diffraction in the phenomenon of acoustic shielding provided by a plate that is periodically perforated with subwavelength slits and immersed in water. We carried out ultrasonic transmission measurements for all directions of propagation in order to check the omnidirectionality of acoustic shielding. While a single slit acts as a Fabry–Perot resonator in the frequency range of interest, the coupling between adjacent slits provides an attenuation frequency band centered around the resonant frequency that is mostly independent of the angle of incidence. Beyond the incident angle of 45 degrees, however, we observe the appearance of scattered radiation that limits the attenuation of ultrasound. This spurious scattering is shown to arise from diffraction by the grating of slits. |
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Keywords: | Fabry–Perot acoustic resonator Acoustic screening Diffraction Acoustic metamaterials Résonateur acoustique de Fabry–Perot Opacité acoustique Diffraction Métamatériaux acoustiques |
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