Journal articles: 'Hydroacoustic signal'

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Tarasov, Sergei, Petr Pivnev, Wenjian Chen, and Dmitry Durov. "Nonlinear acoustics methods in the investigations of elastic wave interactions in the ocean." E3S Web of Conferences 127 (2019): 02017. http://dx.doi.org/10.1051/e3sconf/201912702017.

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Hydroacoustic parametric systems and methods of nonlinear acoustics in the investigation of the Ocean and the Arctic shelf are considered. A short description of the most promising directions of development of hydroacoustic systems with parametric radiating antennas is given. Characteristics of parametric devices are given, and the results of their applications to solve various problems of hydroacoustics are considered. We discuss new opportunities, which appear when applying parametric antennas, to illuminate underwater environment by autonomous underwater vehicles, and to ensure their navigation along the paths. The results of studies demonstrating single-mode excitation of a waveguide in a wide frequency band, of a parametric antenna, are presented. The possibility of broadband signal compression during its propagation in the result of waveguide dispersion, which leads to intensity increase, is shown. The ways of modernization and the prospective of application of the hydroacoustic means, using nonlinear acoustics methods, are discussed.

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Павликов, С. Н., Е. Ю. Копаева, Ю. Ю. Колесов, П. Н. Петров, and А. Н. Крючков. "Hydroacoustic communication method." MORSKIE INTELLEKTUAL`NYE TEHNOLOGII)</msg>, no. 1(55) (March 3, 2022): 208–14. http://dx.doi.org/10.37220/mit.2022.55.1.028.

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Развитие инфокоммуникационных систем требует повышения эффективности использования акустических методов. Однако, совершенствование гидроакустической связи связано с высокой нелинейностью и нестационарностью канала. Происходят раскоорреляция сигнала за счет трансформации в пространстве и во времени. Приемник не видит ожидаемого сигнала с заданными параметрами. Морских интеллектуальных систем кроме радиоволн могут и должны использовать гидроакустические сигналы. В работе предлагается новый способ гидроакустической связи, учитывающий высокие требования к мобильности и пропускной способности инфокоммуникационных технологий морских интеллектуальных систем. Целью работы является повышение качества гидроакустической связи путем тестирования канала и передачи части функций обработки в среду распространения. Актуальность связана с возрастанием требований по увеличению пропускной способности морских интеллектуальных систем между абонентами включая и гидроакустические каналы. Но для этого нужна новая технология, приведенная в данной работе и основанная на повышении помехозащищенности при увеличении допустимых скоростей взаимного перемещения путем увеличения коэффициента взаимной корреляции прошедшего канал и ожидаемого сигнала. Метод решения поставленных задач основан на анализе развития и прогнозировании технологий звукоподводной связи. Новизна заключается в использовании мониторинга передаточной характеристики гидроакустического канала между абонентами с использованием специальных сигналов и методов их обработки. Основные выводы: при незначительных изменениях процессов метода гидроакустического обмена информацией между легитимными абонентами достигнуто повышение качества связи. The development of infocommunication systems requires an increase in the efficiency of the use of acoustic methods. However, the improvement of hydroacoustic communication is associated with high nonlinearity and non-stationarity of the channel. There is a decoorrelation of the signal due to transformation in space and time. The receiver does not see the expected signal with the specified parameters. Marine intelligent systems can and should use sonar signals in addition to radio waves. Vessels, except for research and fishing, do not use hydroacoustics to solve telecommunications problems. The paper proposes a new method of hydroacoustic communication, taking into account the high requirements for mobility and bandwidth of infocommunication technologies of marine intelligent systems. The aim of the work is to improve the quality of hydroacoustic communication by testing the channel and transferring part of the processing functions to the distribution environment. Relevance is associated with the increasing requirements for increasing the capacity of marine intelligent systems between subscribers, including sonar channels. But this requires a new technology, given in this work and based on increasing noise immunity while increasing the permissible speeds of mutual movement by increasing the coefficient of mutual correlation of the past channel and the expected signal. The method of solving the tasks is based on the analysis of the development and forecasting of sound-submarine communication technologies. The novelty lies in the use of monitoring the transfer characteristics of the sonar channel between subscribers using special signals and methods of their processing. The main conclusions: with minor changes in the processes of the method of hydroacoustic exchange of information between legitimate subscribers, an increase in the quality of communication has been achieved.

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Kasatkin, B. A., N. V. Zlobina, S. B. Kasatkin, and G. V. Kosarev. "Spectral-Correlation Signal Processing in the Infrasonic Frequency Range." IOP Conference Series: Earth and Environmental Science 988, no. 3 (February 1, 2022): 032065. http://dx.doi.org/10.1088/1755-1315/988/3/032065.

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Abstract The article discusses hydroacoustic receiving systems, consisting of combined receivers, and the processing of the received hydroacoustic signals. Each module of the sonar system has four channels for receiving information. Spectral processing was carried out using sixteen information parameters, which made it possible to achieve the maximum noise immunity of the receiving system. Correlation processing of signals confirmed the high correlation of signals on the elements of the receiving hydroacoustic system.

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Nejevenko, E. S., and A. A. Sotnikov. "Adaptive modeling for hydroacoustic signal processing." Pattern Recognition and Image Analysis 16, no. 1 (January 2006): 5–8. http://dx.doi.org/10.1134/s1054661806010020.

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Zamarenova, L. N., E. V. Kotel'nikova, and M. I. Skipa. "Energy loss model for hydroacoustic information offshore nets." Electronics and Communications 16, no. 5 (May 29, 2012): 70–74. http://dx.doi.org/10.20535/2312-1807.2011.16.5.247754.

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The power loss model when the signals propagating in the information network hydroacoustic channel on the shelf is considered. The experimental signal propagation power loss data are described by the trend approximated using the functions of the exponential and polynomial type. It is shown that in the case of the signal propagation in the bottom sound channel the trend is described by this approximating functions with the confidence no less than 0,9

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Czapiewska, Agnieszka, Andrzej Luksza, Ryszard Studanski, and Andrzej Zak. "Reduction of the Multipath Propagation Effect in a Hydroacoustic Channel Using Filtration in Cepstrum." Sensors 20, no. 3 (January 29, 2020): 751. http://dx.doi.org/10.3390/s20030751.

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During data transmission in a hydroacoustic channel, one of the problems is the multipath propagation effect, which leads to a decrease in the transmission parameters and sometimes completely prevents it. Therefore, we have attempted to develop a method, which is based on a recorded hydroacoustic signal, that allows us to recreate the original (generated) signal by eliminating the multipath effect. In our method, we use cepstral analysis to eliminate replicas of the generated signal. The method has been tested in simulation and during measurements in a real environment. Additionally, the influence of the method on data transmission in the hydroacoustic channel was tested. The obtained results confirmed the usefulness of the application of the developed method and improved the quality of data transmission by reducing the multipath propagation effect.

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Lillis, Ilse Van, and Olaf Boebel. "Marine soundscape planning: Seeking acoustic niches for anthropogenic sound." Journal of Ecoacoustics 2, no. 1 (March 29, 2018): 1. http://dx.doi.org/10.22261/jea.5gsnt8.

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Both marine mammals and hydroacoustic instruments employ underwater sound to communicate, navigate or infer information about the marine environment. Concurrent timing of acoustic activities using similar frequency regimes may result in (potentially mutual) interference of acoustic signals when both sources are within audible range of the recipient. While marine mammal fitness might be negatively impacted upon, both on individual and population level, hydroacoustic studies may generate low quality data or suffer data loss as a result of bioacoustic interference. This article pursues, in analogy to landscape planning, the concept of marine soundscape planning to reconcile potentially competing uses of acoustic space by managing the anthropogenic sound sources. We here present a conceptual framework exploring the potential of soundscape planning in reducing (mutual) acoustic interference between hydroacoustic instrumentation and marine mammals. The basis of this framework is formed by the various mechanisms by which acoustic niche formation (i.e., the partitioning of the acoustic space) occurs in species-rich communities that acoustically coexist while maintaining high fidelity (hi-fi) soundscapes, i.e., by acoustically partitioning the environment on the basis of time, space, frequency and signal structure. Hydroacoustic measurements often exhibit certain flexibility in their timing, and even instrument positioning, potentially offering the opportunity to minimize the ecological imprint of their operation. This study explores how the principle of acoustic niches could contribute to reduce potential (mutual) acoustic interference based on actual acoustic data from three recording locations in polar oceans. By employing marine soundscape planning strategies, entailing shifting the timing or position of hydroacoustic experiments, or adapting signal structure or frequency, we exemplify the potential efficacy of smart planning for four different hydroacoustic instrumentation types: multibeam echosounders, air guns, RAFOS (Ranging and Fixing of Sound) and tomographic sound sources.

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Kaplun, Dmitry, Alexander Voznesensky, Sergei Romanov, Valery Andreev, and Denis Butusov. "Classification of Hydroacoustic Signals Based on Harmonic Wavelets and a Deep Learning Artificial Intelligence System." Applied Sciences 10, no. 9 (April 29, 2020): 3097. http://dx.doi.org/10.3390/app10093097.

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This paper considers two approaches to hydroacoustic signal classification, taking the sounds made by whales as an example: a method based on harmonic wavelets and a technique involving deep learning neural networks. The study deals with the classification of hydroacoustic signals using coefficients of the harmonic wavelet transform (fast computation), short-time Fourier transform (spectrogram) and Fourier transform using a kNN-algorithm. Classification quality metrics (precision, recall and accuracy) are given for different signal-to-noise ratios. ROC curves were also obtained. The use of the deep neural network for classification of whales’ sounds is considered. The effectiveness of using harmonic wavelets for the classification of complex non-stationary signals is proved. A technique to reduce the feature space dimension using a ‘modulo N reduction’ method is proposed. A classification of 26 individual whales from the Whale FM Project dataset is presented. It is shown that the deep-learning-based approach provides the best result for the Whale FM Project dataset both for whale types and individuals.

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Koltakov, S. A., and A. A. Cherepnev. "HARDWARE-SOFTWARE COMPLEX FOR DIGITAL PROCESSING OF HYDROACOUSTIC SIGNALS." Issues of radio electronics, no. 5 (June 8, 2019): 60–63. http://dx.doi.org/10.21778/2218-5453-2019-5-60-63.

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The article describes the hardware‑software complex (HSC) based on the debugging stand, its composition, modules and operations. A method for synthesizing the output signal is described, a formula and a table of parameters for its calculation are given. Signals and spectra at the input and output of the developed HSC are shown. The obtained parameters of the performance of various agribusiness, based on the signal processor with a General‑purpose processor and two variants with General‑purpose processors. The proposed version of the HSC2–3 times wins in performance compared to the HSC based on the general‑ purpose processor of Intel. This is achieved through the use of modern methods and programming tools, digital signal processing modules, as well as the optimization of the executable code. Recommendations for possible further improvement of the proposed complex are given, which is possible due to the use of modern FPGAs and high‑speed interface.

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Rose, G. A., and W. C. Leggett. "Hydroacoustic Signal Classification of Fish Schools by Species." Canadian Journal of Fisheries and Aquatic Sciences 45, no. 4 (April 1, 1988): 597–604. http://dx.doi.org/10.1139/f88-073.

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Features extracted from hydroacoustic backscatter from fish schools enabled classification by species. Target species were cod (Gadus morhua), capelin (Mallotus villosus), and mackerel (Scomber scombrus), observed in the northern Gulf of St. Lawrence during 1985–86. Two features of internal school density (20 log R amplification) were the best discriminators. These were mean standardized peak to trough distance (SPT) and mean distance between voltage peaks (PP). Quadratic discriminant functions based on the variables SPT, PP, an inverse coefficient of variation, school depth, and off-bottom distance correctly classified 93% of schools (1986). These functions also correctly classified 93% of cod and capelin schools acoustically sampled independently during 1985. The target strength of individual fish was a less successful discriminator of species. For cod and capelin of known length, average target strength (TS) was a linear function of length: TS (decibels) = −65 + 20 log10 length (centimetres). Mackerel had target strengths that were 8–12 dB less than those of cod of equivalent length. Quadratic discriminant functions based on target strength, school depth, and off-bottom distance correctly classified 77% of schools by species. Our methods are generalized to any schooling species or environment.

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Kuznetsov, Mikhail Yu, and Yury A. Kuznetsov. "Hydroacoustic methods and tools for fish stock assessment and fishery maintenance Part 2. Methods and tools of fishery biohydroacoustics." Izvestiya TINRO 184, no. 1 (March 30, 2016): 264–94. http://dx.doi.org/10.26428/1606-9919-2016-184-264-294.

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Studies on influence of hydroacoustic fields on behaviour of commercial species and using of hydroacoustic tools for management of fish and squids behavior to increase the fishing efficiency are overviewed. The methods and means of fisheries biohydroacoustics are considered critically and the reasons of their unsatisfactory using in fishery are analyzed. Sounds with a certain spectrum and level are still applied for influence on fish behaviour without sufficient scientific and technical substantiation, so a complex approach to development of effective hydroacoustic tools for remote control of fish movement is necessary. Results of studies on acoustic reception and acoustic activity for schooling physostomous fishes are presented. Spectral-power and temporal parameters of the sounds and their frequency differentiation by fish size are determined. Sound-generating mechanisms of fish are considered and signal significances of the sounds radiated by fish are recognized. Stereotypes of acoustic behaviour are revealed for toothed whales during their hunting upon fish: these predatory cetaceans have special acoustic manipulators able to generate signals for concentration and holding the fish, adapted for hearing system of the prey. Results of hydrobionic modelling of organs and mechanisms for sound generation of marine animals and their technical realization in hydroacoustic devices are presented. The developed devices allow to generate underwater pulse sound signals simulating biological signals of certain physostomous fish species and predatory cetaceans (dolphins and killer whales). Efficiency of these simulating signals influence on behaviour of fish is proved by behavioral experiments and fishing tests. Applications of these devices for various fisheries are discussed.

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Lubis, Muhammad Zainuddin, Ganda Surya, Kasih Anggraini, and Husnul Kausarian. "PENERAPAN TEKNOLOGI HIDROAKUSTIK DI BIDANG ILMU DAN TEKNOLOGI KELAUTAN." OSEANA 42, no. 2 (November 19, 2019): 34–44. http://dx.doi.org/10.14203/oseana.2017.vol.42no.2.45.

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APPLICATION OF FIELD HYDROACOUSTIC TECHNOLOGY FOR MARINE SCIENCE AND TECHNOLOGY Utilization hydroacoustic methods in recent years have become increasingly effective for estimating the abundance of marine fish, especially fish stocks, where is impossible to do with conventional methods approach. Widely hydroacoustic technology has been used to map and classify the content of the resource base of waters and benthic animals that are on the bottom, type of substrate and benthic biota. Target Strength (TS) is the most important factor in the detection and prediction of fish stocks by using hydroacoustic. The TS is a measure that can describe the ability of a target to reflect sound waves that come about it. In the propagation of sound waves, the amount of energy per second will be flowing through the unit certain area perpendicular to the direction of propagation. The amount of energy per second crossing a certain area of the unit refers to as the intensity of the wave. The system of detection and measurement of underwater involves three components, namely medium, targets, and equipment. Sonar equation is built based on the similarity or balance between the parts of the received signal, the desired (called signal) and the unwanted parts (referred noise or noise), depending on the specific sonar functions are applied.

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Piskur, Pawel, and Marek Gasiorowski. "Digital Signal Processing for Hydroacoustic System in Biomimetic Underwater Vehicle." Naše more 67, no. 1 (March 2020): 14–18. http://dx.doi.org/10.17818/nm/2020/1.3.

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Shirokov, V. A., and V. N. Milich. "Experimental Complex for Studying the Possibilities of Using Hydroacoustic Sensors in Underwater Vision Systems." Vestnik IzhGTU imeni M.T. Kalashnikova 24, no. 4 (2021): 54–64. http://dx.doi.org/10.22213/2413-1172-2021-4-54-64.

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A description of a laboratory experimental and measuring complex is given, including a linear aquatic environment in the form of an extended cylindrical reservoir (hydro wave) and an experimental pool equipped with a system for generating test hydroacoustic signals, a set of electroacoustic and acoustoelectric transducers, and a system for amplifying and digitizing received signals. The results of experimental studies of hydroacoustic piezoelectric sensors and the features of the propagation of the waves generated by them in the described laboratory complex are presented. These results include: an assessment of the sensitivity of sensors, an assessment of the frequency characteristics of sensors, a study of the frequency response of a system of two sensors fixed at the ends of a horizontal hydro-wave guide, a comparison of the results of measurements of the frequency response of sensors in a pipe and a pool, a comparison of signal pulling over time in a pipe and a pool, a study of operation sensors in sonar mode. The most significant results illustrating the behavior of hydroacoustic signals and the potential of the measuring complex are the established possibilities for determining the resonance features of electroacoustic transducers and the detail of the characteristics of the reflection of acoustic signals from objects in an aquatic environment. The main investigated characteristics of hydroacoustic sensors are the sensitivity and frequency characteristics of the investigated sensors, the amplitude-frequency characteristics of the system from the transmitting and receiving transducers, and the features of the transducers' operation in the sonar mode. According to the research results, the characteristics of the sensitivity of the sensors and the assessment of the spread of the sensitivity indicators for representatives of the same type of different parties were obtained. The study of the frequency characteristics of the sensors was focused on the study of the dependence of the module and the phase of the sensor resistance on the frequency and on the determination of the resonance characteristics of the sensors. The presence of resonances (resistance minima) and antiresonances (resistance maxima) in several frequency regions was established. When examining the transducers in sonar mode, a glare structure of echo signals from the components of a complex object (a sphere suspended by a thread), separated by time intervals of 12.3 microseconds, was clearly observed. The delay of the signal reflected from the filament in relation to the signal reflected from the front wall of the sphere is due to the distance by two radii of the sphere, covered by the signal reflected from the filament. Carrying out research in two experimental situations (linear hydro wave and experimental pool) allows assessing the degree of adequacy of the results obtained in the sense of comparing similar experiments in different conditions.

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Shakhtarin, B. I., K. A. Balakhonov, and K. S. Kalashnikov. "OFDM Signal Synchronization Algorithm in the Multipath Hydroacoustic Channel." Journal of Communications Technology and Electronics 63, no. 4 (April 2018): 354–60. http://dx.doi.org/10.1134/s1064226918040113.

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Alekseev, G. G., E. A. Alekseeva, P. V. Galagan, A. P. Sorokin, and S. А. Sorokin. "METHODS FOR IMPLEMENTING NEURAL NETWORK HYDROACOUSTICS ALGORITHMS BASED ON HETEROGENEOUS HARDWARE PLATFORM GRIFON." Issues of radio electronics, no. 5 (June 8, 2019): 48–59. http://dx.doi.org/10.21778/2218-5453-2019-5-48-59.

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Recently, there has been an increase of interest in creating new neural network hydroacoustics algorithms, for example, test sites in the Arctic are being created to evaluate the effectiveness of target detection and to ensure the safety of the Canadian North. The open architecture allows you to adapt hardware to new threats or economic interests. Not only the equipment of radiation and reception of hydroacoustic systems is improved, but also their processing. The article discusses the ways of improvement and the principles of building specialized computers based on the GRIFON hardware platform, providing control and signal processing in mobile and stationary sonar systems. We consider an example of creating a complex that demonstrates the capabilities of the equipment and the prospects for creating calculators with high parameters and minimal mass‑dimensional characteristics. Described in detail the structure and principles of the mathematical software of specialized computer. Comparative characteristics of the proposed algorithms that can be used to optimize signal processing paths and the volume of digital equipment are given.

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Filippov, B. I. "THE CHOICE OF SIGNAL SEPARATION METHOD IN HYDROACOUSTIC CONTROL CHANNEL." Vestnik of Ryazan State Radio Engineering University 66-1 (2018): 29–34. http://dx.doi.org/10.21667/1995-4565-2018-66-4-1-29-34.

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Yan, Huichao, and Linmei Zhang. "Denoising of MEMS Vector Hydrophone Signal Based on Empirical Model Wavelet Method." Proceedings 15, no. 1 (July 8, 2019): 11. http://dx.doi.org/10.3390/proceedings2019015011.

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Underwater acoustic technology is a major method in current ocean research and exploration, which support the detection of seabed environment and marine life. However, the detection accuracy is directly affected by the quality of underwater acoustic signals collected by hydrophones. Hydrophones are efficient and important tools for collecting underwater acoustic signals. The collected signals of hydrophone often contain lots kinds of noise as the work environment is unknown and complex. Traditional signal denoising methods, such as wavelet analysis and empirical mode decomposition, product unsatisfied results of denoising. In this paper, a denoising method combining wavelet threshold processing and empirical mode decomposition is proposed, and correlation analysis is added in the signal reconstruction process. Finally, the experiment proves that the proposed denoising method has a better denoising performance. With the employment of the proposed method, the underwater acoustic signals turn smoothly and the signal drift of the collected hydroacoustic signal is improved. Comparing the signal spectrums of other methods, the spectral energy of the proposed denoising method is more concentrated, and almost no energy attenuation occurred.

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Summerfelt, Steven T., Kyle H. Holland, Joseph A. Hankins, and Martin D. Durant. "A hydroacoustic waste feed controller for tank systems." Water Science and Technology 31, no. 10 (May 1, 1995): 123–29. http://dx.doi.org/10.2166/wst.1995.0368.

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The objective of this work was to develop a commercially viable method to reduce waste feed and thus improve production efficiency and reduce discharge of solids and nutrients within tank based aquaculture systems. We developed and custom fabricated a feeding controller which uses ultrasound to detect uneaten feed and controls feeding events based upon appetite satiation as measured by the quantity of waste feed detected. During feeding, the developed device functions as a combination ultrasonic detector, feedback controller, and interval timer. The device functions as a feedback controller by ultrasonically sampling the stock tank effluent and turning off the feeder when an excessive amount of feed enters the effluent flow. After feeding has been inactivated, the ultrasonic waste feed controller operates as an interval timer and provides a user selected delay between feedings. A custom hydroacoustic probe assembly was developed to detect uneaten feed. The controller can be calibrated by adjusting the transducer signal gain to detect signals resulting from feed pellets, while reducing signals resulting from faeces. The controller has an adjustable set-point for deactivating the feeder circuit based upon the number of feed pellets detected by the transducer and a programmable delay time interval (from 5 to 160 min) to set the time between feedings. The controller also has an adjustable sampling rate for detection at different pipe velocities and an adjustable observation volume for use in standard 2, 3, 4 and 6 inch diameter effluent pipes. The cost in materials and labour to produce this waste feed controller was estimated at around $100 (U.S.).

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Kuz'kin, Venedikt M., Sergey A. Pereselkov, Yury V. Matvienko, Sergey A. Tkachenko, and Dmitry Yu Prosovetskii. "Noise signal detection by horizontal antenna in ocean waveguide." Radioelectronics. Nanosystems. Information Technologies. 14, no. 1 (April 12, 2022): 65–72. http://dx.doi.org/10.17725/rensit.2022.14.065.

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Interferometric processing of hydroacoustic information by using a horizontal linear antenna is described. The detection of a noise source signal is considered by using the Neumann-Pearson criterion. The expressions for the probability of correct detection and false alarm are obtained as dependence on the signal/noise (s/n) ratio and the number of antenna elements. Numerical calculations are performed. The curves of the probability of noise signal detection are given. The efficiency of signal detection by using an antenna in relation to a single receiver is estimated.

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Yuan, Jian, Guang Hu Jin, Jun Li Liu, and Zhong Hai Zhou. "A Hydroacoustic Transponder Based on the Principle of Laser Interferometry." Applied Mechanics and Materials 602-605 (August 2014): 2545–48. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.2545.

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The hydroacoustic transponder based on the principle of laser interferometry is investigated, which consists of three parts: 1) the front-end module, which is a signal receiving and pre-processing module, and consists of a laser interferometric receiver and a filter group; 2) the signal processing module, which consists of the data acquisition module and a data processing system; 3) the back-pulse module, which consists of an automatic gain adjustment module, a transmitter module and a back-transducer. We give the detailed designing flow charts of the hardware and software programs.

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Misiurewicz, Jacek, Konrad Bruliński, Wiesław Klembowski, Krzysztof Stefan Kulpa, and Jan Pietrusiewicz. "Multipath Propagation of Acoustic Signal in a Swimming Pool—Source Localization Problem." Sensors 22, no. 3 (February 3, 2022): 1162. http://dx.doi.org/10.3390/s22031162.

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This paper explores the problem of severe multipath propagation of underwater acoustic signals in a swimming pool. The problem appeared in a study that examined a system used to signal emergency situations (i.e., pre-drowning symptoms detected by a wearable device on a pool user’s wrist) and locate the signal source. A swimming pool acoustic environment is characterized by the presence of large flat reflecting planes surrounding a small volume of water. The reflections are numerous and much stronger than in typical hydroacoustic applications. In this paper, we attempted to create a model of the swimming pool response, one that is suitable for simulation experiments with detection and localization of emergency signals. Then, we explore the possible remedies for the localization system, applied on the transmit side (waveform design) and on the receive side (receiver placement and signal processing). Finally, we present an algorithm for object localization, considering the possible reflections with a multi-hypothesis approach.

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Piskur, Pawel, Piotr Szymak, Krzysztof Jaskólski, Leszek Flis, and Marek Gąsiorowski. "Hydroacoustic System in a Biomimetic Underwater Vehicle to Avoid Collision with Vessels with Low-Speed Propellers in a Controlled Environment." Sensors 20, no. 4 (February 11, 2020): 968. http://dx.doi.org/10.3390/s20040968.

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In this paper, a hydroacoustic system designed for a biomimetic underwater vehicle (BUV) is presented. The Biomimetic Underwater Vehicle No. 2 (BUV2) is a next-generation BUV built within the ambit of SABUVIS, a European Defense Agency project (category B). Our main efforts were devoted to designing the system so that it will avoid collisions with vessels with low-speed propellers, e.g., submarines. Verification measurements were taken in a lake using a propeller-driven pontoon with a spectrum similar to that produced by a submarine propulsion system. Here, we describe the hydroacoustic signal used, with careful consideration of the filter and method of estimation for the bearings of the moving obstacle. Two algorithms for passive obstacle detection were used, and the results are discussed herein.

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Filippov, Boris I. "DETERMINATION OF CHARACTERISTICS OF UNDERWATER AUTONOMOUS APPARATUS TRANSITORY TO THE DOCKING MODULE FOR HNS WITH ULTRASHORT BASE." T-Comm 15, no. 2 (2021): 11–19. http://dx.doi.org/10.36724/2072-8735-2021-15-2-11-19.

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The expediency of creation of the apparatus of the high-frequency hydroacoustic system of transformation in the form of the jointed information and navigation system combined on base of antennas of system in which hydroacoustic navigation systems with ultrashort base can be used is reasonable; it is offered to use signals of data which the docking module and autonomous underwater apparatus exchange by results of measurement of mutual navigation characteristics as navigation. In a point of reception signals are observed reflected from a bottom and surface in the presence of reflecting surfaces which can be with a small depth of water area compared to horizontal distance to SA. The sizes of the reflected signals will depend on effective areas ground and superficial scatterings, which depend on a mutual positioning of DM and SA at the depth of the water area. The spatial correlation of scattered signals renders the greatest influence in the mutual correlation processing of signals from the elements of antenna of HNS. The coefficient of correlation scattered component will be so small that it will give practically no displacement of the bearing estimate at the wave size of the antenna of HNS about 10l. At the small wave sizes of the antenna (commensurable with l) the coefficient of spatial correlation of hindrance can render noticeable influence on the estimate of a difference of phases of a navigation signal from exits of elements of the antenna of HNS. This influence affects especially strongly at estimate of corner of place. The size of the displacement of the estimate will be proportional to the size of the signal reflected from the surface of the water area and coefficient of its spatial correlation. When approaching the SA to the DM, there can be re-reflections of a navigation signal from elements of their constructions. At the radius of a nasal part of SA 0,2 meters the relation of levels will make about 30 dB. Displacement of estimate of difference of phases of signals will be only when there is an angular displacement at reflections (there is not symmetry at a reflection). However, even then influence of the re-reflected signal is small. Considering that the header of the information signal has the same volume of uncorrelated selection as an information signal we receive the relation a signal/hindrance at the input of the decisive scheme, equal 240, that exceeds necessary value for the set accuracy of definition of navigation characteristics.

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Lebert, F., S. Bernardie, and G. Mainsant. "Hydroacoustic monitoring of a salt cavity: an analysis of precursory events of the collapse." Natural Hazards and Earth System Sciences 11, no. 9 (September 29, 2011): 2663–75. http://dx.doi.org/10.5194/nhess-11-2663-2011.

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Abstract. One of the main features of "post mining" research relates to available methods for monitoring mine-degradation processes that could directly threaten surface infrastructures. In this respect, GISOS, a French scientific interest group, is investigating techniques for monitoring the eventual collapse of underground cavities. One of the methods under investigation was monitoring the stability of a salt cavity through recording microseismic-precursor signals that may indicate the onset of rock failure. The data were recorded in a salt mine in Lorraine (France) when monitoring the controlled collapse of 2 000 000 m3 of rocks surrounding a cavity at 130 m depth. The monitoring in the 30 Hz to 3 kHz frequency range highlights the occurrence of events with high energy during periods of macroscopic movement, once the layers had ruptured; they appear to be the consequence of the post-rupture rock movements related to the intense deformation of the cavity roof. Moreover the analysis shows the presence of some interesting precursory signals before the cavity collapsed. They occurred a few hours before the failure phases, when the rocks were being weakened and damaged. They originated from the damaging and breaking process, when micro-cracks appear and then coalesce. From these results we expect that deeper signal analysis and statistical analysis on the complete event time distribution (several millions of files) will allow us to finalize a complete typology of each signal families and their relations with the evolution steps of the cavity over the five years monitoring.

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Tarasov, Sergei, Zhu Jianjun, Petr Pivnev, and Mikhail Gubko. "Low-frequency parametric systems in the shallow sea." E3S Web of Conferences 196 (2020): 02017. http://dx.doi.org/10.1051/e3sconf/202019602017.

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The theoretical model of acoustic wave propagation in the ice-water layer is developed, with, taking into account the velocity dispersion. New opportunities for monitoring the marine environment on long routes, including those covered with ice, are discussed when using parametric sonar antennas. The results of research demonstrating single-mode excitation of a waveguide by a parametric array in a wide frequency band are presented. The possibility of compression of a broadband signal during its propagation, as a result of waveguide dispersion, which leads to an increasing of signal intensity, is shown. The results of experimental studies of the propagation characteristics of a wide-band acoustic signal of a parametric hydroacoustic array in a shallow sea are presented.

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Kasatkin, B. A., N. V. Zlobina, S. B. Kasatkin, D. V. Zlobin, and G. V. Kosarev. "Estimation of Signal Source Direction-Finding and Position Error Using Combined Hydroacoustic Receivers." Giroskopiya i Navigatsiya 27, no. 4 (2019): 117–29. http://dx.doi.org/10.17285/0869-7035.0017.

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Heyburn, Ross, David Bowers, and David N. Green. "Seismic and hydroacoustic observations from recent underwater events in the South Atlantic Ocean." Geophysical Journal International 223, no. 1 (July 20, 2020): 289–300. http://dx.doi.org/10.1093/gji/ggaa291.

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SUMMARY To study the location and characterize two underwater events in the South Atlantic Ocean, we analyse both seismic and hydroacoustic signals. The first event (2017 November 15) occurred around 550 km east of Argentina, near the last reported position of the Argentine Navy submarine the ARA San Juan, the seafloor wreck of which was found one year later. The second event (2017 December 1) was due to an aircraft-dropped depth charge, detonated as part of the search for the ARA San Juan. We use signal arrival times and azimuths recorded at two seismic and two hydroacoustic stations to estimate epicentres for both events; our estimates were within 10 km of the ground-truth locations. We used geophysical models and databases to determine the sound-speed structure of the water and the presence of sea-ice to help interpret differences in the frequency content and dispersion of signals at the two hydrophone stations. Hydrophone signals for the 2017 November 15 event contain significant energy at high frequencies, which is inconsistent with an earthquake source. Hydrophone signals for the 2017 December 1 event show frequency modulations consistent with those expected from the known depth and explosive energy. Hydrophone signals from the 2017 November 15 event also show frequency modulations, though differences between these for the two events suggest differences in the details of the source mechanisms. Using estimates of the local seismic magnitudes, the peak pressures recorded on the hydrophones, and the known charge weight for the 2017 December 1 event, we estimate that the 2017 November 15 event had an acoustic energy release equivalent to around 428 kg of trinitrotoluene. This analysis demonstrates the importance of high-precision traveltime predictions from models of seismic and ocean acoustic velocities when analysing low-magnitude underwater events.

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Ehrenberg, John E., and Thomas C. Torkelson. "FM slide (chirp) signals: a technique for significantly improving the signal-to-noise performance in hydroacoustic assessment systems." Fisheries Research 47, no. 2-3 (July 2000): 193–99. http://dx.doi.org/10.1016/s0165-7836(00)00169-7.

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Campo-Valera, María, Ivan Felis-Enguix, and Isidro Villó-Pérez. "Signal Processing for Parametric Acoustic Sources Applied to Underwater Communication." Sensors 20, no. 20 (October 17, 2020): 5878. http://dx.doi.org/10.3390/s20205878.

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For years, in the field of underwater acoustics, a line of research with special relevance for applications of environmental monitoring and maritime security has been developed that explores the possibilities of non-linear phenomena of sound propagation, especially referring to the so-called parametric effect or self-modulation. This article shows the results of using a new modulation technique based on sine-sweep signals, compared to classical modulations (FSK and PSK). For each of these modulations, a series of 16-bit strings of information with different frequencies and durations have been performed, with the same 200 kHz carrier wave. All of them have been tested in the Hydroacoustic Laboratory of the CTN and, through the application of cross-correlation processing, the limitations and improvements of this novel processing technique have been evaluated. This allows reaching better limits in discrimination of bits and signal-to-noise ratio used in underwater parametric acoustic communications.

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Mizeraczyk, Jerzy, Ryszard Studanski, Andrzej Zak, and Agnieszka Czapiewska. "A Method for Underwater Wireless Data Transmission in a Hydroacoustic Channel under NLOS Conditions." Sensors 21, no. 23 (November 24, 2021): 7825. http://dx.doi.org/10.3390/s21237825.

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Wireless data transmission in the hydroacoustic channel under non-line-of-sight (NLOS) propagation conditions, for example, during a wreck penetration, is difficult to implement reliably. This is mostly due to the multipath propagation, which causes a reduction in the quality of data reception. Therefore, in this work an attempt has been made to develop a reliable method of wireless underwater communication test it under the NLOS conditions. In our method, we used multiple frequency-shift keying (MFSK) modulation, sending a single bit on two carriers, and diversity combining. The method was tested in laboratory conditions which simulated underwater signal propagation during the penetration of the wreck. The propagation conditions were investigated by determining the impulse responses at selected measurement points using the correlation method. Additionally, for comparison, the data transmission quality was determined by the bit error rate (BER) under the same conditions using direct sequence spread spectrum (DSSS) and binary phase shift keying (BPSK) modulation. The obtained results confirmed the usefulness of the application of the developed method for wireless data transmission in a hydroacoustic channel under NLOS conditions.

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Klionskiy, D. M., D. I. Kaplun, M. S. Kupriyanov, A. V. Dorokhov, V. V. Geppener, and A. M. Golubkov. "Vibrational and hydroacoustic signal processing in the frequency domain and its software-hardware implementation." Pattern Recognition and Image Analysis 27, no. 3 (July 2017): 588–98. http://dx.doi.org/10.1134/s1054661817030191.

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Matsumoto, Hiroyuki, Mikhail A. Nosov, Sergey V. Kolesov, and Yoshiyuki Kaneda. "Analysis of Pressure and Acceleration Signals from the 2011 Tohoku Earthquake Observed by the DONET Seafloor Network." Journal of Disaster Research 12, no. 1 (February 1, 2017): 163–75. http://dx.doi.org/10.20965/jdr.2017.p0163.

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Ocean-bottom pressure and acceleration data simultaneously recorded by the DONET seafloor network during the 2011 Tohoku earthquake approximately 800 km from the earthquake epicenter are processed and analyzed. The close location of pressure and acceleration sensors together with the high data-sampling rate enable us to quantitatively examine and interpret pressure variations together with ocean-bottom acceleration for the first time to our knowledge. To interpret observed data, we introduce a set of characteristic frequencies that enable us to identify physical processes responsible for water layer behaviour dependent on the frequency of ocean-bottom oscillations. Explicit formulas are given for calculating all of the characteristic frequencies, which are the basis for introducing nonoverlapping frequency bands, i.e., hydroacoustic waves, forced oscillations, and gravity waves. The physical correctness of such a subdivision is confirmed by the high coherence and nearly zero phase difference between in-situ measured pressure and acceleration variations observed in the forced oscillation frequency band – a band neither hydroacoustic nor gravity waves are generated by ocean-bottom oscillation because the water layer simply follows the ocean bottom, generating forced oscillations. The dominant, long-lasting pressure fluctuations recorded by DONET during the 2011 earthquake are associated with the forced oscillation, or, more precisely, with water and sedimentary layer coupling oscillation. DONET clearly observed the 2011 Tohoku tsunami signal during more than 24 hours following the earthquake. In contrast to DART records, phase dispersion was not manifested in the tsunami signals registered by DONET.

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Filippov, Boris I. "THE CHOICE OF SIGNALS FOR HYDROACOUSTIC NAVIGATION SYSTEM OF TRANSFORMATION UNDERWATER APPARATUS TO DOCKING MODULE." T-Comm 15, no. 6 (2021): 56–64. http://dx.doi.org/10.36724/2072-8735-2021-15-6-56-64.

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The proposed work is the first part of the overall work on the development of the structure of the hydroacoustic navigation system (HNST) for bringing the autonomous underwater vehicle (AUV) to the docking module (DM). The second (final) part will be published in the next issue of the journal. The purpose of this work is to select signals for building HNST providing reduction in a near zone at the distances not exceeding 300 m, an AUV and its docking with the carrier is considered. Mutual definition of a distance and angular position DM of the carrier and AUV relative to each other is carried out for this purpose. Determination of mutual angular coordinates can be carried out with use of HNST with short and ultra-short base. HNST with short base is preferable for realization from the point of view of simplicity. However, its installation on the AUV can be impossible because of rather small sizes of the device, and on AUV should be installed HNST with ultra-short base. HNST with short base can be established on the docking module. Since there are no reasons to assume the high speed of change of the phase characteristic of the developed high-frequency channel of transformation therefore the interval of stationarity of the phase characteristic should be significantly more than duration of a symbol at a speed of transfer of 4 kBit/s. Therefore, it is advisable to exchange measurement data between AUV and DM in the composition of HNST by relative phase modulation (DPSM). Reception of signals is performed by a suboptimal incoherent receiver on which entrance deep restriction of an entrance signal is carried out. The use of deep signal limitation at the receiver input allows to exclude operation of automatic control of strengthening at a stage of entry into communication, as a result, it is possible to reduce the duration of communication sessions. In the combined information navigation system, it is expedient: to apply as navigation signals of data exchanged between AUV and DM based on the results of mutual measurement of navigation parameters; to carry out data exchange between AUV and DM by method DPSM with a speed V = 4 kBit/s; to carry out transfer of the block of data with application of the correcting block cyclic code ; to apply to reception of a block of data diversity reception in combination with majority decoding characters, and then correct errors in the data block with the help of code, and to accompany the issuance of data to the user sign detection code errors in the block.

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Shakhtarin, B. I., V. V. Chudnikov, and R. M. Dyabirov. "Methods of Frequency Synchronization of OFDM Signals in an Underwater Acoustic Channel." Herald of the Bauman Moscow State Technical University. Series Instrument Engineering, no. 4 (127) (August 2019): 62–70. http://dx.doi.org/10.18698/0236-3933-2019-4-62-70.

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Application of signals with orthogonal frequency division multiplexing in underwater communication systems allows efficient use of the information transfer channel bandwidth and thereby increase the carrying capacity of the system. Among the main distinguishing features of the underwater channel there are the relatively low speed of sound propagation in water, multiple reflections from the water surface and the bottom of the reservoir and the Doppler effect, which leads to compression / stretching of the signal in time. The model of the underwater acoustic channel was developed on the assumption that the signal at the receiver input is a superposition of the signals which are copies of the transmitted signal, but passed through different paths from the transmitter. Each signal has its own amplitude, time delay and degree of compression / stretching in time. For correct demodulation of the orthogonal frequency division of the channel-signal, the receiver must first perform time and frequency synchronization. Time synchronization is performed to determine the beginning of the packet and the symbols’ boundaries, and frequency synchronization is necessary for matching the receiver and transmitter sampling frequency to eliminate interchannel interference.For frequency synchronization in a hydroacoustic channel of orthogonal frequency division type, either the preambles invariant to Doppler effect or pilot components of the channel of the orthogonal frequency division type are used. The method based on the synchronization preamble and on a bank of matched filters uses a non-invariant to the Doppler effect preamble at the beginning of the packet. Each filter is matched with a preamble having compression / stretching in time. The autocorrelation method assumes that two identical symbols are included in the transmitted data block for signals with orthogonal frequency division multiplexing, which are used to estimate the scale of signal stretching / compression. The conclusions on the advantages of using orthogonal frequency division multiplexing in an underwater acoustic channel are given.

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Kasatkin, B. A., N. V. Zlobina, S. B. Kasatkin, D. V. Zlobin, and G. V. Kosarev. "Error Estimation of Direction Finding and Determining Coordinates of Signal Source Using Combined Hydroacoustic Receivers." Gyroscopy and Navigation 11, no. 1 (January 2020): 85–93. http://dx.doi.org/10.1134/s2075108720010071.

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Köhler, Andreas, Michał Pętlicki, Pierre-Marie Lefeuvre, Giuseppa Buscaino, Christopher Nuth, and Christian Weidle. "Contribution of calving to frontal ablation quantified from seismic and hydroacoustic observations calibrated with lidar volume measurements." Cryosphere 13, no. 11 (November 26, 2019): 3117–37. http://dx.doi.org/10.5194/tc-13-3117-2019.

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Abstract. Frontal ablation contributes significantly to the mass balance of tidewater glaciers in Svalbard and can be recovered with high temporal resolution using continuous seismic records. Determination of the relative contribution of dynamic ice loss through calving to frontal ablation requires precise estimates of calving volumes at the same temporal resolution. We combine seismic and hydroacoustic observations close to the calving front of Kronebreen, a marine-terminating glacier in Svalbard, with repeat lidar scanning of the glacier front. Simultaneous time-lapse photography is used to assign volumes measured from lidar scans to seismically detected calving events. Empirical models derived from signal properties such as integrated amplitude are able to replicate volumes of individual calving events and cumulative subaerial ice loss over different lidar scan intervals from seismic and hydroacoustic data alone. This enables quantification of the contribution of calving to frontal ablation, which we estimate for Kronebreen to be about 18 %–30 %, slightly below the subaerially exposed area of the glacier front. We further develop a model calibrated for the permanent seismic Kings Bay station (KBS) at about 15 km distance from the glacier front, where 15 %–60 % of calving events can be detected under variable noise conditions due to reduced signal amplitudes at distance. Between 2007 and 2017, we find a 5 %–30 % contribution of calving ice blocks to frontal ablation, which emphasizes the importance of underwater melting (roughly 4–9 m d−1). This study shows the feasibility to seismically monitor not only frontal ablation rates but also the dynamic ice loss contribution continuously and at high temporal resolution.

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Simon, Joel D., Frederik J. Simons, and Guust Nolet. "Multiscale Estimation of Event Arrival Times and Their Uncertainties in Hydroacoustic Records from Autonomous Oceanic Floats." Bulletin of the Seismological Society of America 110, no. 3 (March 17, 2020): 970–97. http://dx.doi.org/10.1785/0120190173.

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ABSTRACT We describe an algorithm to pick event onsets in noisy records, characterize their error distributions, and derive confidence intervals on their timing. Our method is based on an Akaike information criterion that identifies the partition of a time series into a noise and a signal segment that maximizes the signal-to-noise ratio. The distinctive feature of our approach lies in the timing uncertainty analysis, and in its application in the time domain and in the wavelet timescale domain. Our novel data are records collected by freely floating Mobile Earthquake Recording in Marine Areas by Independent Divers (MERMAID) instruments, midcolumn hydrophones that report triggered segments of ocean-acoustic time series.

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Filippov, B. I., and T. B. Trush. "METHOD TO MEASURE SIGNAL DISTRIBUTION DURATION IN HYDROACOUSTIC CHANNEL BASED ON MESSAGES TO SINGLE TIME SCALE." Vestnik of Ryazan State Radio Engineering University 62 (2017): 154–62. http://dx.doi.org/10.21667/1995-4565-2017-62-4-154-162.

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Mashoshin, A. I. "Algorithm for Determining the Coordinates of a Hydroacoustic Source Using the Correlation Function of Its Signal." Acoustical Physics 65, no. 6 (November 2019): 703–10. http://dx.doi.org/10.1134/s1063771019060083.

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Korochentsev, Vladimir, Сhen Wenjian, Victor Petrosyants, Tatiana Lobova, and Julia Shpak. "Investigation of acoustic fields in the arctic zone with uneven ice cover." EPJ Web of Conferences 254 (2021): 02007. http://dx.doi.org/10.1051/epjconf/202125402007.

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A mathematical model for elastic wave propagation in an ice cover with uneven relief (hummock) has been developed. The theoretical model is based on the application of “directed” Green’s functions. We obtained numerical results for different distances between radiating and receiving antennas installed inside the ice layer and in water medium. An information-measuring system was created to investigate elastic acoustic waves along ice surface based on electo-hydraulic generator. Experiments of high-frequency acoustic signal propagation from electro-hydraulic generator in water-ice-air system were carried out. We illustrated the model validity for the investigation of hydroacoustic wave propagation in real ice conditions.

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Vergoz, Julien, Yves Cansi, Yoann Cano, and Pierre Gaillard. "Analysis of Hydroacoustic Signals Associated to the Loss of the Argentinian ARA San Juan Submarine." Pure and Applied Geophysics 178, no. 7 (January 8, 2021): 2527–56. http://dx.doi.org/10.1007/s00024-020-02625-7.

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AbstractOn November 15, 2017, an event related to the disappearance of the Argentine military submarine ARA San Juan was detected by two hydrophone triplet stations of the IMS network, established to enforce the nuclear test ban treaty (CTBT). From the two direct hydroacoustic arrivals recorded at 6000 and 8000 km from the localized wreckage, calculated location based on hydroacoustic data only is poorly constrained, and the associated uncertainties are large. In an attempt to interpret the recorded signals, an air dropped calibration grenade was conducted by the Argentine Navy two weeks later, on December 1, 2017, near the last known position of the submarine. From the comparison of temporal and spectral features of both events, we confirm the impulsive nature of the San Juan event. Array processing was performed with a progressive multi-channel correlation method (PMCC). Fine propagation details of direct arrivals are very well resolved in time-frequency space and thirteen secondary arrivals are revealed for the San Juan event, within the fifteen minutes following direct arrivals. The detections presented in this paper were calculated with DTK-PMCC software embedded in the NDC-In-A-Box virtual machine, and can be reproduced by any CTBTO principal user (Member State user which can access raw waveform data and data bulletins). All the identified late arrivals are associated to reflections or refractions from seamounts, islands and the South American continental Slope. The accurate identification of all the reflectors allows to significantly improve the source location accuracy: 95% confidence ellipse area has been reduced by a factor of 100 compared to location obtained from direct arrivals only, and the estimated location is 3.5 km from the known location of the wreckage. The originality of the relocation method is that it is based on the joint inversion of both San Juan and calibration events unknown parameters, and from the selection of only a well-chosen subset of secondary arrivals. Its calculation did not require either the need of advanced oceanographic specifications, or sophisticated methods requiring heavy computational means. Finally, a detailed cepstral analysis of the direct and secondary arrivals has allowed to detect the existence of a second impulse (doublet) in the signals associated to both San Juan and calibration events. Unlike the calibration event, the anisotropic character of the delays measured from the San Juan cepstra suggests that the 15 November signal was generated by two impulsive acoustic sources closely separated in space and time over scales comparable to the size of the submarine. This study demonstrates the capability of the hydroacoustic component of the IMS network to accomplish its mission of Comprehensive Nuclear-Test-Ban Treaty monitoring.

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Burwen, Debby L., Steven J. Fleischman, James D. Miller, and Mark E. Jensen. "Time-based signal characteristics as predictors of fish size and species for a side-looking hydroacoustic application in a river." ICES Journal of Marine Science 60, no. 3 (January 1, 2003): 662–68. http://dx.doi.org/10.1016/s1054-3139(03)00054-7.

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Abstract Side-looking, fixed-location sonar is used to estimate the abundance of migrating chinook salmon Oncorhynchus tshawytscha in the Kenai River, Alaska. For this application, echo-envelope length has previously been shown to predict fish size better than target strength. Using tethered-fish experiments we generalize these findings to other hydroacoustic descriptors based on time measurements, including range-measurement variability and fish lateral movement. These variables are all descriptors of the echo signal through time. Measurements of these attributes were correlated with daily indices of the species composition of unrestrained fish passing the sonar site. We hypothesize that time-based characteristics are superior predictors of fish size because they capitalize on, or are robust to, the factors which compromise amplitude-based measurements with side-looking sonar.

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Hladkih, Nikita Dmytrovych. "Assessing the impact of the expansion of the Doppler bandwidth for error estimation phase hydroacoustic (HA) signal." Electronics and Communications 17, no. 6 (February 28, 2013): 85–93. http://dx.doi.org/10.20535/2312-1807.2012.17.6.11404.

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Li, Yuxing, Shangbin Jiao, Bo Geng, and Xinru Jiang. "RCMFRDE: Refined Composite Multiscale Fluctuation-Based Reverse Dispersion Entropy for Feature Extraction of Ship-Radiated Noise." Mathematical Problems in Engineering 2021 (December 16, 2021): 1–18. http://dx.doi.org/10.1155/2021/7150921.

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Dispersion entropy (DE), as a newly proposed entropy, has achieved remarkable results in its application. In this paper, on the basis of DE, combined with coarse-grained processing, we introduce the fluctuation and distance information of signal and propose the refined composite multiscale fluctuation-based reverse dispersion entropy (RCMFRDE). As an emerging complexity analysis mode, RCMFRDE has been used for the first time for the feature extraction of ship-radiated noise signals to mitigate the loss caused by the misclassification of ships on the ocean. Meanwhile, a classification and recognition method combined with K-nearest neighbor (KNN) came into being, namely, RCMFRDE-KNN. The experimental results indicated that RCMFRDE has the highest recognition rate in the single feature case and up to 100% in the double feature case, far better than multiscale DE (MDE), multiscale fluctuation-based DE (MFDE), multiscale permutation entropy (MPE), and multiscale reverse dispersion entropy (MRDE), and all the experimental results show that the RCMFRDE proposed in this paper improves the separability of the commonly used entropy in the hydroacoustic domain.

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Timoshevskiy, Mikhail V., and Ivan I. Zapryagaev. "Generation of a wall jet to control unsteady cavitation over a 2D hydrofoil: visualization and hydroacoustic signal analysis." Journal of Physics: Conference Series 899 (September 2017): 032021. http://dx.doi.org/10.1088/1742-6596/899/3/032021.

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WU, Yanchen, and Yingmin WANG. "A research on underwater target recognition neural network for small samples." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 40, no. 1 (February 2022): 40–46. http://dx.doi.org/10.1051/jnwpu/20224010040.

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In the face of the challenges in the field of marine engineering applications in the new era, the goal of automation, high efficiency and accuracy can be achieved by using deep learning-based neural networks in hydroacoustic engineering. However, in the face of objective problems such as the lack of underwater target samples, the complex underwater sound environment, and the poor sample signal-to-noise ratio, the deep learning also becomes less sensitive due to its own limitations. In this paper, by constructing a variety of target feature extraction methods and a deep neural network model, we obtain the target recognition rate network prediction value after matched different target feature extraction with neural network model. Through comparing experimental results, a new idea of solving small sample target identification through deep neural network deep design is proposed.

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Brecht, Dieter, and Lothar Ginzkey. "Contribution to the hydroacoustic ocean monitoring of the UN Test Ban Treaty; signal classification by an autonomous buoy system." Journal of the Acoustical Society of America 107, no. 2 (February 2000): 1049–52. http://dx.doi.org/10.1121/1.428286.

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Fedosov, Valentin, and Andrey Legin. "Wireless data transmission in underwater hydroacoustic environment based on MIMO-OFDM system and application adaptive algorithm at the receiver side." Serbian Journal of Electrical Engineering 16, no. 1 (2019): 71–83. http://dx.doi.org/10.2298/sjee1901071f.

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To increase the transmission speed in wireless data transmission systems, it is necessary to change either the bandwidth or the spectral efficiency, or both simultaneously. Systems based on Multi-Input Multi-Output (MIMO) methods can significantly increase spectral efficiency through parallel transmission using several transmitters and receivers. Such systems are particularly attractive for use in underwater acoustic communications systems, which are normally bandwidth-reduced. MIMO system along with OFDM (Orthogonal Frequency-Division Multiplexing) is a popular technology used in wireless networks to provide a high data transfer rate and resistance to multipath and fading of the channel. The implementation of such a system requires being aware of the channel condition at the receiver, and can be provided by means of using channel parameter estimation schemes. The adaptation task on the receiving side, apart from peak of pattern formation in the direction of the signal expected, also includes the interference-source suppression, that is, the issue of implementing spatial filtering of interference from other directions. However, since the signal and noise direction of arrival are unknown, we get a system with adaptive antenna array (AA). In the proposed research, a phase antenna array was used with controlled weighing.

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Belikov, A. V., S. V. Gagarsky, A. N. Sergeev, S. N. Smirnov, and A. M. Zagorulko. "Study of acoustic signal during laser hydroacoustic processing of biological tissue by microsecond pulses of ytterbium-erbium glass laser radiation." Scientific and Technical Journal of Information Technologies, Mechanics and Optics 18, no. 6 (November 1, 2018): 939–45. http://dx.doi.org/10.17586/2226-1494-2018-18-6-939-945.

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Journal articles on the topic 'Hydroacoustic signal'

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