A measurement principle based on the acousto-optic effect for localization of sound sources has been demonstrated by means of theoretical analysis and experimental results. Despite the difficulties encountered when assembling the experimental setup, the presented acousto-optic beamformer proves to be immune to spatial aliasing. This is a feature that can never be achieved with a transducer array. The presented method not only extends the frequency range of analysis, but it is also a non-invasive technique. Transducer-based methods always require the immersion of a device into the sound field under investigation. This is especially critical at high frequencies, where a large number of transducers are required to avoid spatial aliasing, but at the same time it turns the array into a bulk instrument that can yield scattering effects. The use of light as a sensing element does not influence the sound. There is yet another major difference between the presented acousto-optic beamformer and conventional beamforming techniques. The acousto-optic beamformer is a spatial filter that amplifies sound that propagates perpendicularly to the beam of light, and attenuates otherwise. This means that, unlike conventional beamforming, one has to steer the acousto-optic beamformer physically into a set of different angular directions in order to obtain a complete map of the acoustical space under investigation. Similarly to radar antennas used for air traffic control, the acousto-optic beamformer could in practice rotate at a constant rate, sweeping the different positions of interest. This would not even be required in some particular cases, e.g., surveillance purposes, where it was only necessary to listen to a single direction. Nevertheless, this trade-off does not outshine the advantages of the acousto-optic beamformer.
An acousto-optic beamformer
Journal of the Acoustical Society of America ; 132 , 1 ; 144-149
2012
6 Seiten, 9 Bilder, 21 Quellen
Article (Journal)
English
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