Subwavelength Sound Focusing Using a Time-Reversal Acoustic Sink

Abstract : Time-reversal mirrors (TRM) have been developed since 1986 in order to focus ultrasonic transient waves in complex media. In the last few years, the properties of TR of acoustic fields have been studied in many different areas. Nevertheless, few applications of TR have been developed in audible range acoustics. The aim of this paper is to demonstrate the concept of time-reversal acoustic sink (TRAS) in audible frequency regime, in order to overcome the diffraction limit imposed by the TRM focusing. The major difference between the TRAS and TRM experiments in ultrasonics and audible range is the ratio between the wavelength and the size of the transducers and objects on which the focusing is achieved. The audible range experiment are lead in Fresnel field (near field), whereas the ultrasonic experiments are lead in Fraunhoffer field (far field). We present the first experimental results with a TRAS in this frequency range. The focusing behaviour in a reverberation room using different transient sounds and frequency domains are investigated and discussed, showing that one can take advantage of reverberation in order to achieve subwavelength sound focusing using a single-element TRM. We report that a focal spot of a seventh of a wavelength has been recorded using the TRAS techniques in audible range, compared to the half wavelength obtained with normal TRM processing. A promising application of a numerical TRAS-method in acoustic imaging and localization of acoustic and vibrational sources is presented.
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Contributor : Eric Bavu <>
Submitted on : Wednesday, April 10, 2019 - 5:08:54 PM
Last modification on : Friday, January 10, 2020 - 9:10:03 PM

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  • HAL Id : hal-02095752, version 1

Citation

Eric Bavu, Charles Besnainou, Vincent Gibiat, Julien de Rosny, Mathias Fink. Subwavelength Sound Focusing Using a Time-Reversal Acoustic Sink. Acta Acustica united with Acustica, Hirzel Verlag, 2007, 93 (5), pp.706-715. ⟨hal-02095752⟩

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