Badiey
Mohsen
Badiey
Mohsen
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ArticleTemporal and spatial dependence of a yearlong record of sound propagation from the Canada Basin to the Chukchi Shelf(Acoustical Society of America, 2020-09-23) Ballard, Megan S. ; Badiey, Mohsen ; Sagers, Jason D. ; Colosi, John A. ; Turgut, Altan ; Pecknold, Sean ; Lin, Ying-Tsong ; Proshutinsky, Andrey ; Krishfield, Richard A. ; Worcester, Peter F. ; Dzieciuch, Matthew A.The Pacific Arctic Region has experienced decadal changes in atmospheric conditions, seasonal sea-ice coverage, and thermohaline structure that have consequences for underwater sound propagation. To better understand Arctic acoustics, a set of experiments known as the deep-water Canada Basin acoustic propagation experiment and the shallow-water Canada Basin acoustic propagation experiment was conducted in the Canada Basin and on the Chukchi Shelf from summer 2016 to summer 2017. During the experiments, low-frequency signals from five tomographic sources located in the deep basin were recorded by an array of hydrophones located on the shelf. Over the course of the yearlong experiment, the surface conditions transitioned from completely open water to fully ice-covered. The propagation conditions in the deep basin were dominated by a subsurface duct; however, over the slope and shelf, the duct was seen to significantly weaken during the winter and spring. The combination of these surface and subsurface conditions led to changes in the received level of the sources that exceeded 60 dB and showed a distinct spacio-temporal dependence, which was correlated with the locations of the sources in the basin. This paper seeks to quantify the observed variability in the received signals through propagation modeling using spatially sparse environmental measurements.
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ArticleTemporal sound field fluctuations in the presence of internal solitary waves in shallow water(Acoustical Society of America, 2009-06-19) Katsnelson, Boris G. ; Grigorev, Valery A. ; Badiey, Mohsen ; Lynch, James F.Temporal variations of intensity fluctuations are presented from the SWARM95 experiment. It is hypothesized that specific features of these fluctuations can be explained by mode coupling due to the presence of an internal soliton moving approximately along the acoustic track. Estimates are presented in conjunction with theoretical consideration of the shallow water waveguide.
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ArticleAcoustic multipath arrivals in the horizontal plane due to approaching nonlinear internal waves(Acoustical Society of America, 2011-03-28) Badiey, Mohsen ; Katsnelson, Boris G. ; Lin, Ying-Tsong ; Lynch, James F.Simultaneous measurements of acoustic wave transmissions and a nonlinear internal wave packet approaching an along-shelf acoustic path during the Shallow Water 2006 experiment are reported. The incoming internal wave packet acts as a moving frontal layer reflecting (or refracting) sound in the horizontal plane. Received acoustic signals are filtered into acoustic normal mode arrivals. It is shown that a horizontal multipath interference is produced. This has previously been called a horizontal Lloyd’s mirror. The interference between the direct path and the refracted path depends on the mode number and frequency of the acoustic signal. A mechanism for the multipath interference is shown. Preliminary modeling results of this dynamic interaction using vertical modes and horizontal parabolic equation models are in good agreement with the observed data.
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ArticleMeasurement and modeling of three-dimensional sound intensity variations due to shallow-water internal waves(Acoustical Society of America, 2005-02) Badiey, Mohsen ; Katsnelson, Boris G. ; Lynch, James F. ; Pereselkov, Serguey ; Siegmann, William L.Broadband acoustic data (30–160 Hz) from the SWARM'95 experiment are analyzed to investigate acoustic signal variability in the presence of ocean internal waves. Temporal variations in the intensity of the received signals were observed over periods of 10 to 15 min. These fluctuations are synchronous in depth and are dependent upon the water column variability. They can be explained by significant horizontal refraction taking place when the orientation of the acoustic track is nearly parallel to the fronts of the internal waves. Analyses based on the equations of vertical modes and horizontal rays and on a parabolic equation in the horizontal plane are carried out and show interesting frequency-dependent behavior of the intensity. Good agreement is obtained between theoretical calculations and experimental data.
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ArticleStatistics of nonlinear internal waves during the Shallow Water 2006 Experiment(American Meteorological Society, 2016-04-18) Badiey, Mohsen ; Wan, Lin ; Lynch, James F.During the Shallow Water Acoustic Experiment 2006 (SW06) conducted on the New Jersey continental shelf in the summer of 2006, detailed measurements of the ocean environment were made along a fixed reference track that was parallel to the continental shelf. The time-varying environment induced by nonlinear internal waves (NLIWs) was recorded by an array of moored thermistor chains and by X-band radars from the attending research vessels. Using a mapping technique, the three-dimensional (3D) temperature field for over a month of NLIW events is reconstructed and analyzed to provide a statistical summary of important NLIW parameters, such as the NLIW propagation speed, direction, and amplitude. The results in this paper can be used as a database for studying the NLIW generation, propagation, and fidelity of nonlinear internal wave models.
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ArticleExperimental evidence of three-dimensional acoustic propagation caused by nonlinear internal waves(Acoustical Society of America, 2005-08) Frank, Scott D. ; Badiey, Mohsen ; Lynch, James F. ; Siegmann, William L.The 1995 SWARM experiment collected high quality environmental and acoustic data. One goal was to investigate nonlinear internal wave effects on acoustic signals. This study continues an investigation of broadband airgun data from the two southwest propagation tracks. One notable feature of the experiment is that a packet of nonlinear internal waves crossed these tracks at two different incidence angles. Observed variations for the lower angle track were modeled using two-dimensional parabolic equation calculations in a previous study. The higher incidence angle is close to critical for total internal reflection, suggesting that acoustic horizontal refraction occurs as nonlinear internal waves traverse this track. Three-dimensional adiabatic mode parabolic equation calculations reproduce principal features of observed acoustic intensity variations. The correspondence between data and simulation results provides strong evidence of the actual occurrence of horizontal refraction due to nonlinear internal waves.
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ArticleFrequency dependence and intensity fluctuations due to shallow water internal waves(Acoustical Society of America, 2007-08) Badiey, Mohsen ; Katsnelson, Boris G. ; Lynch, James F. ; Pereselkov, SergueyA theory and experimental results for sound propagation through an anisotropic shallow water environment are presented to examine the frequency dependence of the scintillation index in the presence of internal waves. The theory of horizontal rays and vertical modes is used to establish the azimutal and frequency behavior of the sound intensity fluctuations, specifically for shallow water broadband acoustic signals propagating through internal waves. This theory is then used to examine the frequency dependent, anisotropic acoustic field measured during the SWARM'95 experiment. The frequency dependent modal scintillation index is described for the frequency range of 30–200 Hz on the New Jersey continental shelf.
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ArticleAnalysis and modeling of broadband airgun data influenced by nonlinear internal waves(Acoustical Society of America, 2004-12) Frank, Scott D. ; Badiey, Mohsen ; Lynch, James F. ; Siegmann, William L.To investigate acoustic effects of nonlinear internal waves, the two southwest tracks of the SWARM 95 experiment are considered. An airgun source produced broadband acoustic signals while a packet of large nonlinear internal waves passed between the source and two vertical linear arrays. The broadband data and its frequency range (10–180 Hz) distinguish this study from previous work. Models are developed for the internal wave environment, the geoacoustic parameters, and the airgun source signature. Parabolic equation simulations demonstrate that observed variations in intensity and wavelet time–frequency plots can be attributed to nonlinear internal waves. Empirical tests are provided of the internal wave-acoustic resonance condition that is the apparent theoretical mechanism responsible for the variations. Peaks of the effective internal wave spectrum are shown to coincide with differences in dominant acoustic wavenumbers comprising the airgun signal. The robustness of these relationships is investigated by simulations for a variety of geoacoustic and nonlinear internal wave model parameters.
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ArticlePassive time reversal acoustic communications through shallow-water internal waves(IEEE, 2010-11-30) Song, Aijun ; Badiey, Mohsen ; Newhall, Arthur E. ; Lynch, James F. ; DeFerrari, Harry A. ; Katsnelson, Boris G.During a 12-h period in the 2006 Shallow Water Experiment (SW06), binary phase shift keying (BPSK) signals at the carrier frequencies of 813 and 1627 Hz were propagated over a 19.8-km source–receiver range when a packet of strong internal waves passed through the acoustic track. The communication data are analyzed by time reversal processing followed by a single-channel decision feedback equalizer. Two types of internal wave effects are investigated in the context of acoustic communications. One is the rapid channel fluctuation within 90-s data packets. It can be characterized as decreased channel coherence, which was the result of fast sound-speed perturbations during the internal wave passage. We show its effect on the time reversal receiver performance and apply channel tracking in the receiver to counteract such fluctuation. The other one is the long-term (in the scale of hours) performance degradation in the depressed waveguide when the internal waves passed through the acoustic track. Even with channel tracking, the time reversal receiver experiences average 3–4-dB decrease in the output signal-to-noise ratio (SNR). Such long-term performance degradation is explained by the ray approximation in the depressed waveguide.