Layer filtering for seafloor scatterers imaging

Abstract

The image source method in acoustics is well known to simulate reverberation. It has also been recently used for characterization of seafloor sound-speed structure. The idea is to detect image sources by imaging techniques to obtain information about the environment. In this paper, the idea is to use the detection of image sources to remove reflections from plane interfaces in recorded signals and perform imaging with this filtered signal. This imaging process highlights scatterers because their wave front shapes are different than those from plane interfaces. Applications can be in seafloor buried object detection or scattering analysis from interface roughnesses or volume heterogeneities.

The image‐source method: a tool for geoacoustic inversion

“…The travel time of an image source located at the coordinate r is . From this fundamental difference between wave reflection over a plane interface and the scattering by heterogeneities, it is possible to filter interface echoes from the received signal (Pinson and Holland ). Once image sources are detected, their contribution to the received signal is subtracted so that buried scatterers in the sediment can be detected.…”

“…(c) Same as (b) using signals with subtracted image‐source echoes. Source : Reproduced from Pinson and Holland (), with the permission of the Acoustical Society of America.…”

“…Due to this simple representation of interface reflections with image sources, it has been possible to extend the ISM to include layer‐interface dip angles (Pinson and Holland , ) and to estimate the SSP measurement uncertainties due to noise and interface roughnesses (Pinson, Guillon and Cervenka ; Pinson ). Also, the image‐source concept can be exploited in another way, that is, to separate the two effects of wave reflection (from interfaces) and scattering (from heterogeneities) by subtracting the image‐source echoes to image seafloor heterogeneities or buried scatterers (Pinson and Holland ).…”

Imaging shallow gas migration pathways in a mud‐volcano province using an autonomous underwater vehicle (Malta Plateau, Mediterranean Sea)

“…Borcea et al . () and Pinson and Holland () have proposed layer filtering algorithms to highlight scatterers by taking advantage of the wave front shape differences between an interface reflection and a scattered wave by an object. In our experiment geometry, the hydrophone array aperture is too small to differentiate those wavefront shapes, therefore an approach is employed related to synthetic aperture processing, but with a higher tolerance to sensor coordinate uncertainties.…”