Theory of acoustic daylight imaging revisited
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Acoustic Daylight Imaging: Vision in the Ocean
Sound provides a natural means for exploring the ocean but current sonar systems, as used for example in swath-mapping applications, do not provide directly pictorial images of the ocean depths. Such systems are more akin to radar, which relies on travel-time information to map the environment. A new acoustic technique for providing real-time visual images of the interior of the ocean is curren...
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Acoustic Daylight is a new technique for creating pictorial images of undersea objects from the acoustic illumination provided by the ambient noise field. As in conventional photography, the directionality of the illumination affects the contrast in the image through the shadows that are cast. Three aspects of the directionality, or anisotropy, of ambient noise in the ocean are discussed in thi...
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The acoustic time history of the sun’s surface is a stochastic t x y -cube of information. Helioseismologists cross-correlate these noise traces to produce impulse response seismograms, providing the proof of concept for a long-standing geophysical conjecture. We pack the x y -mesh of time series into a single super-long one-dimensional time series. We apply Kolmogoroff spectral factorization t...
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Ambient noise can be used to produce images of submerged objects using the mean intensity of the backscattered energy, a technique coined ‘‘acoustic daylight’’ because of its direct analogy to vision. It is suggested that there may be substantial additional information in higher moments of the data. At high frequencies ~.10 kHz!, absorption suppresses long-range propagation so that a received s...
متن کاملTheory of Daylight/Interferometric Imaging: Tutorial
I present the theory of interferometric imaging (II). Interferometric imaging is any algorithm that images crosscorrelated data for the reflectivity or source distribution. As examples, I show that II can image arbitrary reflectivity distributions by migrating ghost reflections in passive seismic data, generalize the receiver-function imaging method used by seismologists, and migrate free-surfa...
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