Time-reversal focusing of elastic surface waves

Norville, Pelham D.; Scott, Waymond R.

doi:10.1121/1.1945468

Cited by 16 publications

(9 citation statements)

References 15 publications

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“…The results of estimation are also close to the experiment. There is a small difference between the experimental waveform and that calculated with the use of approximate equation (12) and practically full coincidence for that calculated from Eq. (13).…”

Section: Comparison Of Predicted Tra-focused Field With Experimentsmentioning

confidence: 78%

“…7(a) shows the form of TRA-focused signal observed in the experiment and Fig. 7(b) the form of calculated signal according to approximate formula (12). It is seen that the TRA-focused wave form calculated according to Eq.…”

Section: Comparison Of Predicted Tra-focused Field With Experimentsmentioning

confidence: 94%

“…The TRA Focusing Systems (TRA FS) are able to focus and stir ultrasound beams in a 3D volume using just a few piezoceramic transducers glued to the facets of a solid (aluminum) block. The TRA FS can be applied to biomedical imaging [4][5][6], nondestructive testing [7][8][9][10], and land mine detection [11][12][13]. The prediction of the TRA-focused signals and the formation of the focused signals with desired form and frequency content is important for these and other TRA FS applications.…”

Section: Introductionmentioning

confidence: 99%

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Ultrasonic focused waveform generation using time reversal acoustic focusing system

et al. 2008

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The concept of Time Reversal Acoustics (TRA) provides an elegant possibility of both temporal and spatial concentrating of acoustic energy in highly inhomogeneous media. We explored the possibility of generating acoustical signals with arbitrary waveforms using the TRA Focusing System (TRA FS). A method has been developed to predict TRAfocused ultrasound waveforms and spatial distribution by using the measurements of transfer function of transfer function relating the signal at the TRA transmitter to that at the focusing point.The developed approach for TRA-focused signal waveform prediction from the results of direct signal measurements was tested on ten-channel TRA FS based on aluminum resonator with glued piezotransducers. The TRA FS operated in the frequency band of 100-1000 kHz.The formation of ultrasonic signals with various envelopes was demonstrated experimentally. The calculated and experimentally measured waveforms and spatial distributions were practically identical. We formed triangular, rectangular, and amplitude modulated tone burst signals with different modulation frequencies in the focal region. The level of side lobes in the generated signals was much lower than that for standard TRA focusing.

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Section: Comparison Of Predicted Tra-focused Field With Experimentsmentioning

confidence: 78%

Section: Comparison Of Predicted Tra-focused Field With Experimentsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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Ultrasonic focused waveform generation using time reversal acoustic focusing system

et al. 2008

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“…This simple observation has provided very promising techniques in a variety of domains including biomedical imaging [22], seismology [33], material analysis [37], land-mine detection [35], telecommunication [34] and underwater acoustics [21]. In time-reversal algorithms, an output wave is time reversed and retransmitted into the medium.…”

Section: Introductionmentioning

confidence: 99%

Time-reversal algorithms in viscoelastic media

et al. 2013

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In this paper, we consider the problem of reconstructing sources in a homogeneous viscoelastic medium from wavefield measurements. We first present a modified timereversal imaging algorithm based on a weighted Helmholtz decomposition and justify mathematically that it provides a better approximation than by simply time reversing the displacement field, where artifacts due to the coupling between the pressure and shear waves appear. Then, we investigate the source inverse problem in an elastic attenuating medium. We provide a regularized time-reversal imaging which corrects the attenuation effect at the first order. The results of this paper yield the fundamental tools for solving imaging problems in elastic media using cross correlation techniques.

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“…This desire stems from the use of time reversal to enhance the response of buried objects by focusing seismic energy in time and space. [7][8][9][10] Norville and Scott 11 report an experimental study of time-reversal focusing of elastic surface waves scattered by a buried object. In that work, they also describe an algorithm for estimating the surface motion detected by the LDVs by iterative convolution of an appropriate Green's function with the response due to each source.…”

Section: Introductionmentioning

confidence: 99%

Green’s functions for a volume source in an elastic half-space

Zabolotskaya¹,

Ilinskii²,

Hay³

et al. 2012

The Journal of the Acoustical Society of America

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Green's functions are derived for elastic waves generated by a volume source in a homogeneous isotropic half-space. The context is sources at shallow burial depths, for which surface (Rayleigh) and bulk waves, both longitudinal and transverse, can be generated with comparable magnitudes. Two approaches are followed. First, the Green's function is expanded with respect to eigenmodes that correspond to Rayleigh waves. While bulk waves are thus ignored, this approximation is valid on the surface far from the source, where the Rayleigh wave modes dominate. The second approach employs an angular spectrum that accounts for the bulk waves and yields a solution that may be separated into two terms. One is associated with bulk waves, the other with Rayleigh waves. The latter is proved to be identical to the Green's function obtained following the first approach. The Green's function obtained via angular spectrum decomposition is analyzed numerically in the time domain for different burial depths and distances to the receiver, and for parameters relevant to seismo-acoustic detection of land mines and other buried objects.

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Time-reversal focusing of elastic surface waves

Cited by 16 publications

References 15 publications

Ultrasonic focused waveform generation using time reversal acoustic focusing system

Ultrasonic focused waveform generation using time reversal acoustic focusing system

Time-reversal algorithms in viscoelastic media

Green’s functions for a volume source in an elastic half-space

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