title: Nondestructive imaging of shallow buried objects using acoustic computed tomography.
abstract: The nondestructive three-dimensional acoustic tomography concept of the present investigation combines computerized tomography image reconstruction algorithms using acoustic diffracting waves together with depth information to produce a three-dimensional (3D) image of an underground section. The approach illuminates the underground area of interest with acoustic plane waves of frequencies 200-3000 Hz. For each transmitted pulse, the reflected-refracted signals are received by a line array of acoustic sensors located at a diametrically opposite point from the acoustic source line array. For a stratified underground medium and for a given depth, which is represented by a time delay in the received signal, a horizontal tomographic 2D image is reconstructed from the received projections. Integration of the depth dependent sequence of cross-sectional reconstructed images provides a complete three-dimensional overview of the inspected terrain. The method has been tested with an experimental system that consists of a line array of four-acoustic sources, providing plane waves, and a receiving line array of 32-acoustic sensors. The results indicate both the potential and the challenges facing the new methodology. Suggestions are made for improved performance, including an adaptive noise cancellation scheme and a numerical interpolation technique.
authors.affiliation: Department of Electrical and Computer Engineering, University of Western Ontario, London, Canada.
authors.forename: Waheed A
authors.initials: WA
authors.lastname: Younis
authors.forename: Stergios
authors.initials: S
authors.lastname: Stergiopoulos
authors.forename: David
authors.initials: D
authors.lastname: Havelock
authors.forename: Julius
authors.initials: J
authors.lastname: Grodski
mesh_terms: D000162:Acoustics; D000465:Algorithms; D006801:Humans; D013997:Time Factors; D014057:Tomography, X-Ray Computed