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Search results for: ACOUSTIC ANALYSIS
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Acoustic and Flow Aspects of Novel Synthetic Jet Actuator
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Modelling of acoustic heating induced by different types of sound
PublicationWyprowadzono równanie dynamiczne sterujące ogrzewaniem na skutek strat energii fali akustycznej dowolnego typu, okresowej i nieokresowej, w płynie ze standardową dyssypacją i przewodnictwem ciepła. Zbadano efektywność ogrzewania w przypadku dźwięku stochastycznego i regularnego.
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Electrochemical and acoustic emission studies of aluminium pitting corrosion
PublicationBadania metodą potencjokinetyczną i emisjii akustycznej przeprowadzono w typowej trójelektrodowej celce elektrochemicznej. Elektrodę badaną przygotowano z stopu aluminium 1050A. Badania metodą cyklicznej polaryzacji i emisjii akustycznej wykonywano jednocześnie. Na podstawie wyników akustycznych i polaryzacyjnych wyznaczono potencjał korozji wzerowej.
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Search for the fundamental solution to the vector acoustic wave equations
PublicationCzasowo-przestrzenna funkcja Greena pola swobodnego jest dobrze znanym rozwiązaniem podsta-wowym skalarnego niejednorodnego równania falowego. Wyraża ona odpowiedź ośrodka płynnego na punktowe zaburzenie o symetrii sferycznej. Odpowiedź ośrodka na zaburzenie wektorowe nie jest tak oczywista. Artykuł przedstawia oryginalne podejście do problemu, polegające na systematycznej, szcze-gółowej weryfikacji hipotetycznych rozwiązań skalarnych...
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Application of acoustic emission in evaluation of pitting corrosion insteel
PublicationPrzedstawiono przegląd różnych zastosowań emisji akustycznej (AE) w badaniach korozji wżerowej stali austenitycznej. Wykorzystanie emisji akustycznej w przypadku tego rodzaju korozji nie jest przypadkowe, ponieważ korozja wżerowa jest najgroźniejszym typem korozji, atakującym różne materiały konstrukcyjne takie jak stal. Prezentowana praca przeglądowa dostarcza przydatnych informacji o naturze pomiarów akustycznych, które wykazują...
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Acoustic streaming caused by modulated sound and wave packets.
PublicationRozpatruje się powstanie pola wirowego na skutek nieliniowej propagacji fali akustycznej w środowiskach z lepkością. Teoria odwołuje się do fal akustycznych nieokresowych, w odróżnieniuod teorii klasycznej. Obliczenia numeryczne na podstawie nowych wzorów są porównywane z wynikami teorii klasycznej.
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Pressure distribution and beam pattern of the parametric acoustic arrays.
PublicationPrzedstawiono model matematyczny i wyniki badań teoretycznych zjawiska oddziaływań fal dla źródeł parametrycznych. Model matematyczny zbudowano w oparciu o równanie KZK. Do rozwiązania zagadnienia zastosowano metodę różnic skończonych. Badano zmiany ciśnienia fal wybranych częstotliwości w obrębie wiązki akustycznej oraz charakterystyki kierunkowe dla kołowych źródeł parametrycznych generujących fale różnych częstotliwości.
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Procesing the complex signal in the acoustic processor of a sonobuoy system
PublicationW artykule przedstawiono metody cyfrowego przetwarzania sygnału kompleksowego w procesorze akustycznym systemu radiohydroboi. Omówiono ogólną postać systemu oraz sygnału kompleksowego. Opisano dwie alternatywne metody przetwarzania sygnału: pierwszą w dziedzinie czasu, drugą w dziedzinie częstotliwości. Zaprezentowano schematy blokowe algorytmów obu sposobów przetwarzania. Omówiono problemy praktycznej realizacji poszczególnych...
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Signal conditioning for examination of shallow-water acoustic noise correlation properties
PublicationThe article describes the process of signal conditioning for examination of acoustic noise correlation properties in shallow water. Knowledge of these properties is very important for the design processes of passive and active hydroacoustic systems. This paper focuses on the above issue from the point of view of passive sonar. In sonar systems, signal processing algorithms operate on both useful acoustic signals, and accompanying...
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Analysis of Impulse Responses Measured in Motion in a Towing Tank
PublicationThe growing interest in developing autonomous underwater vehicles (AUVs) and creating underwater sensor networks (USNs) has led to a need for communication tools in underwater environments. For obvious reasons, wireless means of communication are the most desirable. However, conducting research in real conditions is troublesome and costly. Moreover, as hydroacoustic propagation conditions change very significantly, even during...
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Analysis of Impulse Responses Measured in Motion in a Towing Tank
PublicationThe growing interest in developing autonomous underwater vehicles (AUVs) and creating underwater sensor networks (USNs) has led to a need for communication tools in underwater environments. For obvious reasons, wireless means of communication are the most desirable. However, conducting research in real conditions is troublesome and costly. Moreover, as hydroacoustic propagation conditions change very significantly, even during...
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Introduction to the special issue on machine learning in acoustics
PublicationWhen we started our Call for Papers for a Special Issue on “Machine Learning in Acoustics” in the Journal of the Acoustical Society of America, our ambition was to invite papers in which machine learning was applied to all acoustics areas. They were listed, but not limited to, as follows: • Music and synthesis analysis • Music sentiment analysis • Music perception • Intelligent music recognition • Musical source separation • Singing...
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Suitability of acoustic power amplifiers as power amplifiers in underwater communication systems
PublicationThe paper presents selected acoustic power amplifiers from among those currently available. The results of a series of measurements characterising the amplifiers are presented. The measured amplitude and phase characteristics as a function of frequency for four selected amplifiers are analysed. The spectra of the output signal in the band from 4 kHz to 30 kHz are presented. The usefulness of the selected amplifiers in an underwater...
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Thermal Self-Action of Acoustic Beams Containing Several Shock Fronts
PublicationThermal self-action of an acoustic beam with one discontinuity or several shock fronts is studied in a Newtonian fluid. The stationary self-action of a single sawtooth wave with discontinuity (or some integer number of these waves), symmetric or asymmetric, is considered in the cases of self-focusing and self- defocusing media. The results are compared with the non-stationary thermal self-action of the periodic sound. Thermal self-action...
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Nonlinear Modeling in Time Domain Numerical Analysis of Stringed Instrument Dynamics
PublicationMusical instruments are very various in terms of sound quality with their timbre shaped by materials and geometry. Materials' impact is commonly treated as dominant one by musicians, while it is unclear whether it is true or not. The research proposed in the study focuses on determining influence of both these factors on sound quality based on their impact on harmonic composition. Numerical approach has been chosen to allowed independent...
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Developing assumptions for the tram noise attenuation passive system using the noise maps analysis method
PublicationThe paper presents experimental research carried out to determine the possible actions to reduce thenoise generated by trams in a highly urbanised area. A few design strategies affecting tram ride qualityhave been presented – especially in the aspect of the acoustic phenomena. Main sources of the noisein trams were characterised. The paper includes selected results of comprehensive...
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Multiple-Input Multiple-Output Technique for Underwater Acoustic Communication System
PublicationThe performance of an underwater acoustic communication (UAC) system is limited due to tough propagation conditions in the UAC channel. Multiple-Input Multiple-Output (MIMO) technique can improve the reliability of the data transmission system, increase its speed, increase its range, and reduce the energy consumption. The paper presents an implementation method of MIMO technique in the form of coding the Space-Time Block Code and...
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Impact of Boundary Conditions on Acoustic Excitation of EntropyPerturbations in a Bounded Volume of Newtonian Gas
PublicationExcitation of the entropy mode in the field of intense sound, that is, acoustic heating, is theoreticallyconsidered in this work. The dynamic equation for an excess density which specifies the entropy mode,has been obtained by means of the method of projections. It takes the form of the diffusion equation withan acoustic driving force which is quadratically nonlinear in the leading order. The diffusion coefficient isproportional...
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Thermal self-action effects of acoustic beam in a vibrationally relaxing gas
PublicationThermal self-action of acoustic beam in a molecular gas with excited internal degrees of molecules’ freedom, is studied. This kind of thermal self-action differs from that in a Newtonian fluid. Heating or cooling of a medium takes place due to transfer of internal vibrational energy. Equilibrium and non-equilibrium gases, which may be acoustically active, are considered. A beam in an acoustically active gas is self-focusing unlike...
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Performance of Coherent Modulation Scheme Used in Acoustic Underwater Communication System
PublicationThe development of an acoustic underwater communication system for shallow waters is still a big scientificand construction challenge. Currently, non-coherent modulations in combination with strong channel coding are used to achieve reliable communication with low rate in such a channel. To obtain transmission with a higher transmission rate, it is required to use coherent modulation. This paper presents the assumptions of such...
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Decomposition of Acoustic and Entropy Modes in a Non-Isothermal Gas Affected by a Mass Force
PublicationDiagnostics and decomposition of atmospheric disturbances in a planar flow are considered in this work. The study examines a situation in which the stationary equilibrium temperature of a gas may depend on the vertical coordinate due to external forces. The relations connecting perturbations are analytically established. These perturbations specify acoustic and entropy modes in an arbitrary stratified gas affected by a constant...
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Wake-Up Receiver for Underwater Acoustic Communication Using in Shallow Water
PublicationA data frame transmitted over the underwater acoustic channel usually begins with a preamble. Therefore, underwater communication systems have a dedicated receiver that constantly listens to the preamble signals. A receiver that is to work effectively in shallow waters must have solutions that effectively reduce the impact of the permanently occurring multipath propagation. The article presents a solution based on complementary...
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Comparison of Acoustic and Visual Voice Activity Detection for Noisy Speech Recognition
PublicationThe problem of accurate differentiating between the speaker utterance and the noise parts in a speech signal is considered. The influence of utilizing a voice activity detection in speech signals on the accuracy of the automatic speech recognition (ASR) system is presented. The examined methods of voice activity detection are based on acoustic and visual modalities. The problem of detecting the voice activity in clean and noisy...
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Modeling of performance of a AUV vehicle towards limiting the hydro-acoustic field.
PublicationSome results of research devoted to the modeling of a AUV-Stealth vehicle performance towards limiting its hydro-acoustic field are presented in the paper. At the beginning the AUV-Stealth autonomous underwater vehicle concept is described. Then the method of research is introduced. Next the key design drivers of the AUV-Stealth vehicle are presented. Between them are the AUV-Stealth hull form, arrangement of internal spaces,...
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Standing Waves and Acoustic Heating (or Cooling) in Resonators Filled with Chemically Reacting Gas
PublicationStanding waves and acoustic heating in a one-dimensional resonator filled with chemically reacting gas, is the subject of investigation. The chemical reaction of A ! B type, which takes place in a gas, may be reversible or not. Governing equations for the sound and entropy mode which is generated in the field of sound are derived by use of a special mathematical method. Under some conditions, sound waves propagating in opposite...
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Testing the Wide-Sense Stationarity of Bandpass Signals for Underwater Acoustic Communications
PublicationThe Underwater Acoustic Communication (UAC) systems work in communication channels characterized by a large variety of multipath propagation conditions that can additionally change over time. Designing a reliable communication system requires knowledge of the transmission parameters of the channel. There is a need for the development of adaptive signaling schemes that would dynamically optimize the signal parameters of the physical...
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Extended duration running and impulse loading characteristics of an acoustic bearing with enhanced geometry
PublicationThis paper presents performance during prolonged running of the acoustic bearing when PZTs are switched off and when they are switched on. The effect of active PZT on shaft’s displacements in X and Y directions is clearly demonstrated. Performance of the acoustic bearing was also assessed when an impulse force was applied to the running shaft at speed. Once again the benefits of having PZTs active are beyond doubt. The instability...
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STUDY OF SEASONAL ACOUSTIC PROPERTIES OF SEA WATER IN SELECTED WATERS OF THE SOUTHERN BALTIC
PublicationClimate Research of the globe is a current task, in particular to confirm the general hypothesis of global warming associated with an increase in average temperature. The sea acoustic climate is derived from the concept of climate and refers to the conditions of propagation of acoustic waves in a particular basin. In this paper, the results of systematic measurements of temperature, salinity and velocity distributions of sound...
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Investigations of pitting corrosion of magnesium by means of DEIS and acoustic emission
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Application of Vector Sensors to Acoustic Surveillance of a Public Interior Space
PublicationPrzedstawiono metodę precyzyjnej detekcji i lokalizacji źródeł dźwięku w pomieszczeniach. Wykorzystano wektorowe czujniki akustyczne, dostarczające sygnałów ciśnienia akustycznego i prędkości cząsteczek powietrza. Zaprezentowano metodę lokalizacji źródeł dźwięku na widowni wydarzenia publicznego. Przedstawiono demonstracyjny system zainstalowany w sali wykładowej. System poddano ocenie dokładności na podstawie przeprowadzonych...
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Searching for objects under the sea bed bythe acoustic method
PublicationOpisano metodykę poszukiwania przedmiotów zamulonych w morzu z zastosowaniem metod akustycznych.
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Green turtle and fish identification based on acoustic target strength
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Underwater acoustic communications system with error correction and synchronization coding
PublicationNiezawodna transmisja danych w wielodrogowym i niestacjonarnym płytkim kanale podwodnym wymaga zastosowania efektywnej techniki modulacji oraz equalizacji adaptacyjnej. W zaproponowanym artykule w systemie transmisji danych zastosowano modulację OFDM oraz equalizację adaptacyjną opartą o filtrację Kalmana. Ponadto zaimplementowano dwie techniki kodowania: FEC w celu eliminacji błędów transmisji oraz kodowanie pseudoszumowe, którego...
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The estimation of norwegian cod size distribution from acoustic data
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Acoustic and Flow Aspects of Synthetic Jet Actuators with Chevron Orifices
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Acoustic signal processing in passive sonar system with towed array
PublicationW referacie opisano przetwarzanie sygnałów akustycznych w pasywnym systemie hydrolokacyjnym. W pojęciu ''przetwarzanie sygnałów akustycznych'' mieszczą się wszelkie operacje wykonywane na sygnałach analogowych tj. wzmacnianie, filtracja i próbkowanie, jak również operacje na sygnałach cyfrowych uzyskanych w procesie próbkowania. Do operacji cyfrowych wykonywanych w systemie zalicza się synchronizację, konwersję, sortowanie, wytwarzanie...
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On intermolecular potential determination via equations of state and by acoustic data
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Synchronization system for underwater acoustic communications using in shallow waters
PublicationA reliable synchronization system of the transmitted data frame has a significant impact on the efficiency of the underwater communication system. This applies in particular to communication systems dedicated to work in shallow waters, where the phenomenon of multipath permanently occurs. To overcome these difficulties, the concept of a synchronization system consisting of two broadband signals of opposite monotonicity was presented....
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Acoustic radiation force and streaming caused by non periodic acousticsource.
PublicationTeoria i obliczenia numeryczne przepływu rotacyjnego (''streamingu'') towarzyszącemu fali akustycznej w przepływach lepkich nieliniowych. Fala wywołująca może być nieokresowa: impulsowa lub paczka falowa itd. Przykład pojedynczego pulsu rozpatrywany. Ilustracje delikatnej struktury czasowej powstania fal rotacyjnych przedstawione na rysunkach.
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Liquid water. Analytical equation of state and acoustic parameters evaluation.
PublicationRównanie stanu dla ciekłej wody zaproponowane przez Jefferya - Austina zastosowano do obliczeń prędkości dźwięku oraz parametru nieliniowości B/A. Parametry akustyczne są porównywane z danymi doświadczalnymi.
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Modeling of active fiber Bragg grating underwater acoustic sensor.
PublicationW pracy przedstawiono wyniki modelowania nowego typu przetwornika hydroakustycznego wykorzystującego światłowodową siatkę Bragga. Siatka ta, domieszkowana jonami pierwiastków ziem rzadkich, pracuje jako laser z rozłożonym sprzężeniem zwrotnym, co pozwala na znaczne zwiększenie czułości tego prztwornika w porównaniu z rozwiązaniami wykorzystującymi siatki pasywne. W celu uzyskania równomiernego rozkładu naprężeń siatki zastosowano...
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A novel approach to bottom scattering using a narrow acoustic beam.
PublicationPrzedstawiono model opisujący w prosty sposób rozpraszanie sygnału akustycznego na dnie morskim jako filtr liniowy z odpowiedzią impulsową o zmieniającej się w czasie chwilowej dominującej częstotliwości. Przedyskutowano pasujący do tego modelu przypadek zbioru punktowych rozpraszaczy równomiernie rozmieszczonych na powierzchni dna, w tym wpływ takich parametrów jak głębokość oraz odległość pomiędzy rozpraszaczami.
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Application of passive acoustic radar to automatic localization, tracking and classification of sound sources
PublicationA concept, practical realization and applications of the passive acoustic radar to automatic localization, tracking and classification of sound sources were presented in the paper. The device consists of a new kind of multichannel miniature sound intensity sensors and a group of digital signal processing algorithms. Contrary to active radars, it does not emit the scanning beam but after receiving surrounding sounds it provides...
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ADAPTIVE IDENTIFICATION OF TIME-VARYING IMPULSE RESPONSE OF UNDERWATER ACOUSTIC COMMUNICATION CHANNEL
PublicationThe transmission properties of underwater acoustic communication channel can change dynamically due to the movement of acoustic system transmitter and receiver or underwater objects reflecting transmitted signal. The time-varying impulse response measurement and estimation are necessary to match the physical layer of data transmission to instantaneous channel propagation conditions. Using the correlative measurement method, impulse...
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Calibration of acoustic vector sensor based on MEMS microphones for DOA estimation
PublicationA procedure of calibration of a custom 3D acoustic vector sensor (AVS) for the purpose of direction of arrival (DoA) estimation, is presented and validated in the paper. AVS devices working on a p-p principle may be constructed from standard pressure sensors and a signal processing system. However, in order to ensure accurate DoA estimation, each sensor needs to be calibrated. The proposed algorithm divides the calibration process...
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Automatic sound source localization in disturbing conditions using acoustic vector sensors
PublicationA concept, practical realization and applications of a passive acoustic radar to automatic localization and tracking of sound sources in disturbing conditions were presented in the paper. The device consists of the new kind of multichannel miniature sound intensity sensors and a group of digital signal processing algorithms. The sensitivity of the realized acoustic radar was examined in free sound field. Several kinds of sound...
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MSIS sonar image segmentation method based on underwater viewshed analysis and high-density seabed model
PublicationHigh resolution images of Mechanically Scanned Imaging Sonars can bring detailed representation of underwater area if favorable conditions for acoustic signal to propagate are provided. However to properly asses underwater situation based solely on such data can be challenging for less than proficient interpreter. In this paper we propose a method to enhance interpretative potential of MSIS image by dividing it in to subareas depending...
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Rough Set Based Modeling and Visualization of the Acoustic Field Around the Human Head
PublicationThe presented research aims at modeling acoustical wave propagation phenomena by applying rough set theory in a novel manner. In a typical listening environment sound intensity is determined by numerous factors: a distance from a sound source, signal levels and frequencies, obstacles’ locations and sizes. Contrarily, a free-field is characterized by direct, unimpeded propagation of the acoustical waves. The proposed approach is...
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Standing Acoustic Waves and Relative Nonlinear Phenomena in a Vibrationally Relaxing Gas-Filled Resonator
PublicationStanding acoustic waves in one-dimensional resonator filled with vibrationally relaxing gas, are studied. Two regimes of excitation of molecular vibrational degrees of freedom are considered, equilibrium and nonequilibrium. The acoustic energy enlarges with time in the non-equilibrium regime and decreases otherwise before formation of discontinuity. After that, it decreases due to nonlinear absorption and tends to zero in equilibrium...
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Problem of proper decomposition and initialization of acoustic and entropy modes in a gas affected by the mass force
PublicationThe relations connecting perturbations specific for acoustic and entropy modes in an accelerated fluid or in a fluid affected by constant mass force, are derived. They allow to decompose the total vector of perturbations and the overall energy into acoustic and non-acoustic parts uniquely at any instant. In order to do this, three quantities are required, for example total perturbations in entropy, pressure and velocity. The evaluations...