Acoustic resonators for far-field control of sound on a subwavelength scale |
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Authors: | Lemoult Fabrice Fink Mathias Lerosey Geoffroy |
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Institution: | Institut Langevin, ESPCI ParisTech, France. |
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Abstract: | We prove experimentally that broadband sounds can be controlled and focused at will on a subwavelength scale by using acoustic resonators. We demonstrate our approach in the audible range with soda cans, that is, Helmholtz resonators, and commercial computer speakers. We show that diffraction-limited sound fields convert efficiently into subdiffraction modes in the collection of cans that can be controlled coherently in order to obtain focal spots as thin as 1/25 of a wavelength in air. We establish that subwavelength acoustic pressure spots are responsible for a strong enhancement of the acoustic displacement at focus, which permits us to conclude with a visual experiment exemplifying the interest of our concept for subwavelength sensors and actuators. |
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