Japanese Journal of Applied Physics · 2006 · 27 citations · 8 references
Natural SciencesMarine EngineeringOcean EngineeringAcousticsOcean AcousticsUnderwater AcousticsAcoustic ImagingAcoustic MeasurementAcoustic SensingAcoustic Sensing SystemsOcean Ambient NoiseUnderwater Sound PropagationAcoustic Field TheoryAcoustic LensingAcoustic NoiseFinite Difference Time Domain ModelingFinite Difference Time Domain SimulationUnderwater Acoustic ImagingUnderwater Imaging SystemsUnderwater Target Detection
Much attention has been paid to the new idea of detecting objects using ocean ambient noise. This concept is called ambient noise imaging (ANI). In this study, sound fields focused by an acoustic lens system constructed with a single biconcave lens were analyzed using the finite difference time domain (FDTD) method for realizing an ANI system. The size of the lens aperture that would have sufficient resolution–for example, the beam width is 1° at 60 kHz–was roughly determined by comparing the image points and -3 dB areas of sound pressure fields generated by lenses with various apertures. Then, in another FDTD analysis, we successfully used a lens with a determined aperture to detect rigid target objects in an acoustic noise field generated by a large number of point sources.
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Imaging the ocean with ambient noise
Michael J. Buckingham, Broderick V. Berknout, Stewart Glegg · Nature · 1992 · 173 citations