Comparison and visualization of focusing wave fields from various time reversal techniques in elastic media

Anderson, Brian E.; Ulrich, Timothy J.; Bas, Pierre‐Yves Le

doi:10.1121/1.4828980

Cited by 11 publications

(3 citation statements)

References 18 publications

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“…and thus there will be some added color to the resulting focal signal. The added color can be described as a ringing, or multiple converging wave fronts as recently shown by Anderson et al [24]. However, this added coloring will be significantly reduced for the IF results as we will show in our experiments.…”

Section: Deconvolution As An Inverse Filtersupporting

confidence: 53%

Improving spatio-temporal focusing and source reconstruction through deconvolution

et al. 2015

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In this study, a technique is demonstrated to improve the ability of time reversal to both spatially and temporally focus, or compress, elastic wave energy, or to improve the quality of the reconstruction of the source signal. This method utilizes the deconvolution, or inverse filter, in single channel time reversal experiments in solids. Special attention is given to the necessary procedure for improving source signal reconstruction in real experimental conditions. It is also demonstrated theoretically and numerically that good temporal focusing implies that the radius in the spherically symmetric part of the spatial focus is small.

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Section: Deconvolution As An Inverse Filtersupporting

confidence: 53%

Improving spatio-temporal focusing and source reconstruction through deconvolution

et al. 2015

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“…The equivalence suggests application to the cross‐correlation function of the signal processing methods originally developed for deterministic wavefields. In particular, the C3F technique bears similarity to well‐known wavefront reversal and back propagation [ Tappert et al ., ; Fink , ; Anderson et al ., ] and mode separation [ Xu et al ., ] methods normally applied to deterministic wavefields.…”

Section: Discussionmentioning

confidence: 99%

Interferometry of infragravity waves off New Zealand

et al. 2014

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Wave interferometry is a remote sensing technique, which is increasingly employed in helioseismology, seismology, and acoustics to retrieve parameters of the propagation medium from twopoint cross-correlation functions of random wavefields. Here we apply interferometry to yearlong records of seafloor pressure at 28 locations off New Zealand's South Island to investigate propagation and directivity properties of infragravity waves away from shore. A compressed cross-correlation function technique is proposed to make the interferometry of dispersive waves more robust, decrease the necessary noise averaging time, and simplify retrieval of quantitative information from noise cross correlations. The emergence of deterministic wave arrivals from cross correlations of random wavefields is observed up to the maximum range of 692 km between the pressure sensors in the array. Free, linear waves with a strongly anisotropic distribution of power flux density are found to be dominant in the infragravity wavefield. Lowest-frequency components of the infragravity wavefield are largely isotropic. The anisotropy has its maximum in the middle of the spectral band and decreases at the high-frequency end of the spectrum. Highest anisotropy peaks correspond to waves coming from portions of the New Zealand's shoreline. Significant contributions are also observed from waves propagating along the coastline and probably coming from powerful sources in the northeast Pacific. Infragravity wave directivity is markedly different to the east and to the west of the South Island. The northwest coast of the South Island is found to be a net source of the infragravity wave energy.

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“…TR focuses waves to a selected location that converge from all directions to produce the focus, and then diverge from that location. 13 The divergence of the waves after TR focusing may be considered a virtual source. 14 To achieve the highest possible amplitude of TR focusing several methods are explored here, including deconvolution (or inverse filtering), one-bit, clipping, and decay compensation.…”

Section: Introductionmentioning

confidence: 99%

Time reversal focusing of high amplitude sound in a reverberation chamber

Willardson

Anderson

Young

et al. 2018

The Journal of the Acoustical Society of America

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Time reversal (TR) is a signal processing technique that can be used for intentional sound focusing. While it has been studied in room acoustics, the application of TR to produce a high amplitude focus of sound in a room has not yet been explored. The purpose of this study is to create a virtual source of spherical waves with TR that are of sufficient intensity to study nonlinear acoustic propagation. A parameterization study of deconvolution, one-bit, clipping, and decay compensation TR methods is performed to optimize high amplitude focusing and temporal signal focus quality. Of all TR methods studied, clipping is shown to produce the highest amplitude focal signal. An experiment utilizing eight horn loudspeakers in a reverberation chamber is done with the clipping TR method. A peak focal amplitude of 9.05 kPa (173.1 dB peak re 20 μPa) is achieved. Results from this experiment indicate that this high amplitude focusing is a nonlinear process.

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Comparison and visualization of focusing wave fields from various time reversal techniques in elastic media

Cited by 11 publications

References 18 publications

Improving spatio-temporal focusing and source reconstruction through deconvolution

Improving spatio-temporal focusing and source reconstruction through deconvolution

Interferometry of infragravity waves off New Zealand

Time reversal focusing of high amplitude sound in a reverberation chamber

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