Understanding the feedback effect through the physics of the diffraction-based sensitivity kernel for a target in shallow water: A small-scale experimental demonstration - Archive ouverte HAL Access content directly
Journal Articles Journal of the Acoustical Society of America Year : 2011

Understanding the feedback effect through the physics of the diffraction-based sensitivity kernel for a target in shallow water: A small-scale experimental demonstration

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Christian Marandet
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  • PersonId : 922608
Philippe Roux
Patrick La Rizza
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Abstract

Using the feedback effect, we experimentally detect a wavelength-sized target in a shallow ultrasonic waveguide between two source-receiver transducers on acoustic feedback. The waveguide represents a 1-km-long, 50-m-deep ocean acoustic channel at the 1/1000 scale. The feedback phenomenon, or Larsen effect, occurs when a source and a receiver are connected both acoustically through the propagation medium and electrically through an amplifier in such a way that the received signal is simultaneously and continuously added to the emitted signal. A resonance is obtained when the emitter and the receiver are in phase. This resonance is very sensitive to any change in the medium which makes it a good observable for target detection. In presence of a target in the waveguide, the numerical gain of the feedback effect has to increase in order to compensate the scattering of the acoustic field from the target. In a separate experiment, the scattered field may also be recorded in a transmission configuration from the same couple of emitter/receiver with an impulse as a source signal. A comparison is made between the two different approaches.
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Dates and versions

insu-00680986 , version 1 (20-03-2012)

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Christian Marandet, Philippe Roux, Patrick La Rizza, Barbara Nicolas. Understanding the feedback effect through the physics of the diffraction-based sensitivity kernel for a target in shallow water: A small-scale experimental demonstration. Journal of the Acoustical Society of America, 2011, 130 (4), p.2410. ⟨10.1121/1.3654662⟩. ⟨insu-00680986⟩
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