Active Nonlinear Acoustic Sensing of an Object with Sum or Difference Frequency Fields

Zhang, Wenjun; Liu, Yuming; Ratilal, Purnima; Cho, Byunggu; Makris, Nicholas C.

doi:10.3390/rs9090954

Cited by 6 publications

(9 citation statements)

References 46 publications

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“…Refs. [11,23] studied the generation of f s from two primary signals only (which can be useful due to its high spatial resolution and accuracy), but here we also analyzed its maximization. The results of this work showed that we could obtain much higher amplitudes of f s by slightly reducing one of the primary frequencies (see Section 3).…”

Section: Methodsmentioning

confidence: 99%

“…These techniques rely on the detection of transmitted or reflected ultrasonic waves. They use the signals emitted from the source (primary frequencies) during the entire process [6], which falls under the linear theory valid for infinitesimal pressure amplitudes, or consider combinations of the source signals such as harmonics, difference frequencies, sum frequencies, subharmonics [7][8][9][10][11], which falls under the nonlinear theory (at least second-order terms) valid for finite pressure amplitudes. The benefits of the signal produced at the difference frequency by parametric arrays stand in its low attenuation and high directivity.…”

Section: Introductionmentioning

confidence: 99%

“…The wavelength of this sum-frequency signal is shorter than the ones of the source and difference frequencies. This particularity is very attractive when a high resolution or accuracy of the results is required, as for example in medical imaging or nondestructive testing [10,11].…”

Section: Introductionmentioning

confidence: 99%

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Nonlinear Maximization of the Sum-Frequency Component from Two Ultrasonic Signals in a Bubbly Liquid

Sastre

Vanhille

2019

Sensors

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Techniques based on ultrasound in nondestructive testing and medical imaging analyze the response of the source frequencies (linear theory) or the second-order frequencies such as higher harmonics, difference and sum frequencies (nonlinear theory). The low attenuation and high directivity of the difference-frequency component generated nonlinearly by parametric arrays are useful. Higher harmonics created directly from a single-frequency source and the sum-frequency component generated nonlinearly by parametric arrays are attractive because of their high spatial resolution and accuracy. The nonlinear response of bubbly liquids can be strong even at relatively low acoustic pressure amplitudes. Thus, these nonlinear frequencies can be generated easily in these media. Since the experimental study of such nonlinear waves in stable bubbly liquids is a very difficult task, in this work we use a numerical model developed previously to describe the nonlinear propagation of ultrasound interacting with nonlinearly oscillating bubbles in a liquid. This numerical model solves a differential system coupling a Rayleigh–Plesset equation and the wave equation. This paper performs an analysis of the generation of the sum-frequency component by nonlinear mixing of two signals of lower frequencies. It shows that the amplitude of this component can be maximized by taking into account the nonlinear resonance of the system. This effect is due to the softening of the medium when pressure amplitudes rise.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nonlinear Maximization of the Sum-Frequency Component from Two Ultrasonic Signals in a Bubbly Liquid

Sastre

Vanhille

2019

Sensors

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“…Wide area scattering strength images were produced by beamforming, matched filtering and charting the received OAWRS returns and then correcting for transmission loss (Andrews, Gong, & Ratilal, ; Gong et al., ; Jagannathan et al., ; Makris et al., , ; Naftali & Makris, ). Linear frequency modulated (LFM) source waveform transmissions of 50 Hz bandwidth and 1‐s duration centred at 955 Hz were used for the OAWRS cod measurements presented, which are above but within a decade of the expected swimbladder scattering resonance frequencies (Blaxter & Batty, ; Gong et al., ; Jagannathan et al., ; Jain et al., ; Love, ; Løvik & Hovem, ; Zhang, Liu, Ratilal, Cho, & Makris, ) of spawning cod in this region. Scattering strength was converted to areal population density by calibration with local in situ measurements of areal population density obtained from vertical echo sounding.…”

Section: Methodsmentioning

confidence: 99%

Instantaneous areal population density of entire Atlantic cod and herring spawning groups and group size distribution relative to total spawning population

Makris

Godø

et al. 2018

Fish and Fisheries

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The wide‐area group behaviour of spawning Atlantic cod and herring is investigated. By a combination of Ocean Acoustic Waveguide Remote Sensing (OAWRS) and conventional sensing methods, first‐look images of the instantaneous population density are obtained of entire Atlantic cod spawning groups, stretching for tens of kilometres in the Nordic Seas. This structural information made it possible to quantify the spawning group size distribution of cod over a roughly 30‐year period from conventional line‐transect data acquired annually by vertical echo sounding in the Nordic Seas. The size distribution is found to be consistent with the log‐normal probability density often found in growth processes that depend on many independent parameters. Nordic Seas cod populations are found to distribute into many vast behavioural groups during spawning with relatively stable mean size despite larger variations in total annual population. When sustained at pre‐industrial levels, the total spawning population is found to greatly exceed the mean spawning group size. As an apparent consequence of this large differential, when the total population, or overall scale, declined to within a standard deviation of this mean cod spawning group quantum, or inner‐group‐behavioural scale, return to pre‐industrial levels required decades. Findings for Atlantic herring are similar, where summing the spawning group populations measured in a single instantaneous OAWRS image per day over the 8‐day peak spawning period enabled accurate enumeration of the entire Georges Bank herring spawning population to within 7% of the independent NOAA estimate for 2006. These results may be relevant to other oceanic fish.

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“…For inhomogeneities with zero forward direction velocity, the Doppler spread term and the amplification factor vanishes, and so the modal field-temporal-covariance coefficient reduces to Eqs. (5) and (8) of ref. 26 .…”

Section: Analytic Expressions For the Mean And Temporal Correlation Omentioning

confidence: 99%

Predicting the Effects of Random Ocean Dynamic Processes on Underwater Acoustic Sensing and Communication

Cho

Makris

2020

Sci Rep

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Acoustics is the primary means of sensing and communication in the ocean for humans and many marine animals. Natural fluctuations in the ocean, however, degrade these abilities in ways that have been previously difficult to forecast. Here, we address this issue by predicting sensing and communication degradation in terms of acoustic attenuation, dispersion and temporal decorrelation at typical operational ranges and frequencies in continental-shelf environments. This is done with analytic expressions derived from first physical principles. The analytic expressions provide the statistics of the acoustic field after forward propagating through an ocean waveguide containing 3-D random inhomogeneities from the independent or combined effects of rough sea-surfaces, nearsea-surface air bubbles and internal waves. The formulation also includes Doppler effects caused by the inhomogeneities' random horizontal motion, enabling modeling and prediction over a wide range of environments and frequencies. Theoretical predictions are confirmed with available acoustic measurements in several continental-shelf environments using standard oceanographic measurements for environmental support. We quantify how the acoustic signals decorrelate over timescales determined by the underlying temporal coherence of ocean dynamic processes. Surface gravity waves and near-sea-surface air bubbles decorrelate acoustic signals over seconds or less, whereas internal waves affect acoustic coherence at timescales of several to tens of minutes. Doppler spread caused by the inhomogeneities' motion further reduces acoustic temporal coherence, and becomes important at the high frequencies necessary for communication and fine-scale sensing. We also show that surface gravity waves and bubbles in high sea states can cause increasingly significant attenuation as frequency increases. The typical durations of marine mammal vocalizations that carry over great distances are found to be consistent with the coherence timescales quantified here and so avoid random distortion of signal information even by incoherent reception. Acoustics is the primary means of sensing and communication in the ocean for applications in such diverse areas as ocean resource management, marine ecology, climatology, oceanography and national defense 1-9. This is due to the severe attenuation of electromagnetic waves in water 3. Current ocean sensing limitations make marine resource management challenging. Without significant improvements in ocean sensing it will be difficult to address the unprecedented decline in many oceanic species recently described and predicted by the United Nations 10. Many marine animals also use acoustics to communicate, navigate, and locate food 11-13. Natural fluctuations and resulting inhomogeneities in the ocean such as surface waves, internal waves and bubbles, however, can significantly degrade acoustic sensing and communication abilities 14-18 by introducing attenuation, dispersion and coherence losses that limit operational ranges, time windows and freq...

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Active Nonlinear Acoustic Sensing of an Object with Sum or Difference Frequency Fields

Cited by 6 publications

References 46 publications

Nonlinear Maximization of the Sum-Frequency Component from Two Ultrasonic Signals in a Bubbly Liquid

Nonlinear Maximization of the Sum-Frequency Component from Two Ultrasonic Signals in a Bubbly Liquid

Instantaneous areal population density of entire Atlantic cod and herring spawning groups and group size distribution relative to total spawning population

Predicting the Effects of Random Ocean Dynamic Processes on Underwater Acoustic Sensing and Communication

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