Acoustical imaging with bending waves based on sparse inversion

Abstract

Bending waves can be employed in the context of acoustical imaging for the detection of material defects or localization of vibration sources. The obtainable spatial resolution is limited by the minimal wavelength contained in the excitation signal. The evanescent part of the wave field can usually not be used for the imaging of sources at distances exceeding a wavelength. Therefore only the propagating part of the field can be employed, which means that the minimum size of the region where energy can be focused is in the order of half a wavelength due to the diffraction limit. If the recovery of vibration sources and reflections is posed as an inverse problem, regularization techniques can be applied in order to force a sparse solution. Preliminary results indicate that the assumption of a sparse source distribution can be used to resolve features significantly smaller than half a wavelength. The approach is therefore applied as a high-resolution imaging technique for bending wave fields.