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Tytuł:
Spatial distributions of acoustic field scattered at the sea bottom-numerical model
Autorzy:
Tęgowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/332620.pdf
Data publikacji:
1997
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The results of the numerical simulation of acoustic wave scattering from rough and attenuating sea bottom are presented. Seattering is studied using ray theory with the main geometry of model taken from Novarini and Caruthers. The distribution of rough surface heights together with bottom acoustical parameters determine the scattered acoustical field properties. Different bottom types with various acoustical parameters have been used in numerical calculations in order to examine the influence of phase shift of reflected signal on scattered acoustical field. Simulation technique was made for surfaces with normal distribution of heights and standard deviation of the surface elevation, 0.01 m. Spatial distribution of the scattered field parameters was determined. Results of calculations for frequencies between 5 and 100 kHz and various bottom parameters are compared.
Źródło:
Hydroacoustics; 1997, 1; 141-146
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fractal characterisation of 30 kHz echoes from southern Baltic bottom
Autorzy:
Tęgowski, J.
Łubniewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/331844.pdf
Data publikacji:
2000
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The fractal dimension of 30 kHz echo envelope is used for characterise the bottom sediment type in Southern Baltic Sea. Two methods of the echo waveform fractal dimension calculation were applied: the autocorrelation function log-log slope method and the power spectrum log-log slope method. The results are presented and compared. They show that fractal dimension of echo envelope describes well the bottom sediments morphology and may be used as a significant descriptor in the remote sea bed classification procedures.
Źródło:
Hydroacoustics; 2000, 3; 15-18
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of ship motion on acoustic remote sensing
Autorzy:
Tegowski, J.
Zielinski, A.
Powiązania:
https://bibliotekanauki.pl/articles/332057.pdf
Data publikacji:
2003
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
ship motion
acoustic remote sensing
Opis:
Ship motion affects quality of acoustic data collected by various acoustic remote sensing systems used for bottom and fisheries surveying. The angular position of an acoustic beam changes in time from its nominal position vertical to sea surface. This motion affects the acoustic returns from the bottom and other targets by changing their intensity and arrival times. In this paper we illustrate these effects on bottom returns obtained using single beam sonar.
Źródło:
Hydroacoustics; 2003, 6; 205-214
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of some echo parameters to the seabed classification - methodological analysis
Autorzy:
Tęgowski, J.
Łubniewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/332378.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The paper presents the methodological analysis of acoustical seabed classification procedure, which aim is to define the most appropriate bottom echo parameters as an input set. Several acoustical and statistical features of echo envelope were compared with morphological features of bottom sediments and a set of parameters was proposed: integral backscattering strength, time of reverberation, radius of autocorrelation, fractal dimension, moment of inertia, and skewness. It was shown using real echoes from seafloor, that this set may be a good descriptor of sea bottom sediments and may be used in classification procedures. In addition, the spatial distribution of echo skewness within Polish Economical Zone of Baltic Sea was presented as an example and compared with sediments allocation map.
Źródło:
Hydroacoustics; 2001, 4; 237-240
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synthesis and wavelet analysis of side-scan sonar sea bottom imagery
Autorzy:
Tęgowski, J.
Zieliński, A.
Powiązania:
https://bibliotekanauki.pl/articles/332396.pdf
Data publikacji:
2006
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
A backscattered side-scan sonar signal contains indirect information about the scattering surface, namely, the bottom sediment, character of bottom surface, and seafloor relief. This paper presents a method of automatic estimation of height of seafloor characteristic objects and micro relief reconstruction applying the measured shadow length. The proposed method utilises coefficients of two-dimensional discrete wavelet decomposition of a side-scan sonar image as the input to the self-organised neural network classification algorithm. The heights of seafloor characteristic objects were the basis for synthesis of a three-dimensional map of the bottom surface. The computations were conducted for data recorded in Hornsund Fjord (Spitsbergen Island, Svalbard Archipelago) during a habitat mapping experiment and for synthetic data. The verification of the proposed algorithm was made by comparison of computed results with calibrated video recordings.
Źródło:
Hydroacoustics; 2006, 9; 199-208
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Use of the Hilbert-Huang Transform for characterization of gassy sediments in Eckernförde Bay
Autorzy:
Tęgowski, J.
Ostrovsky, I.
Zamaryka, M.
Powiązania:
https://bibliotekanauki.pl/articles/331774.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The bottom top layer of the central part of the Eckernförde Bay (Germany) consists of soft muddy sediments containing free methane gas. Locations of gas bubbles trapped in the sediment and gas seeps visualised with hydroacoustic data have been reported. The main goal of our study was to examine whether it was possible, using a singlebeam echosounder with relatively high frequency of the transmitted signal (120 kHz), to detect echo properties that could be indicative of the occurrence of free gas in the bottom sediments. During three days of measurements organised by Leibniz Institute of Marine Sciences (IFM-GEOMAR) in Kiel (Germany), the acoustic data were collected from boards of r/v Polarfuchs and r/v Littorina. The Hilbert-Huang Transform was applied to detect ‘gassy’ anomalies in backscattered signals from the bottom. The transformer decomposes signal into finite and small number of Intrinsic Mode Function (IMF) components with time-dependent amplitudes and frequencies. Certain IMF components carry information on variability of geoacoustic parameters, which can be indicative of presence of gas bubbles in the acoustically penetrated sediment as well as in the water column. Based on the shape of the echo signal envelope and its fading with range we characterized the signal attenuation in areas where gas was present. The rapid increase in acoustical wave attenuation in areas of intensive gas ebullition demonstrates good applicability of the method proposed.
Źródło:
Hydroacoustics; 2011, 14; 237-244
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The acoustic evidence for gas bubbles in the lake Kinneret sediments
Autorzy:
Tęgowski, J.
Ostrovsky, I.
Zamaryka, M.
Powiązania:
https://bibliotekanauki.pl/articles/332021.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The changes in gas content of bottom sediments are associated with rapid alterations of the ambient conditions (climate change, eutrophication, water level fluctuation, etc). In this paper we present results of acoustical measurements of sound scattering at gassy sediments in the subtropical Lake Kinneret (Sea of Galilee), where the 120 kHz single beam echosounder for bottom recognition was used. Measurements were carried out over a 10-year period along 14 standard transects. The echo parameterization method was applied to study acoustical features of bottom deposits and their variability in relation to sedimentary content of gas bubbles. Particularly, we examined the influence of water level fluctuations, affecting the presence of gas bubbles in the surface sediments on sound scattering and echo envelope parameters (spectral, wavelet, fractal, statistical and energetic). Presented results indicate the usefulness of the proposed method of backscattered signals processing for monitoring of the seafloor features.
Źródło:
Hydroacoustics; 2010, 13; 261-268
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Extraction of seabed geomorphologic features of Svalbard fjords using high-resolution side scan sonar
Autorzy:
Tęgowski, J.
Giżejewski, J.
Zieliński, A.
Powiązania:
https://bibliotekanauki.pl/articles/331637.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
Svalbard fjords
side scan sonar
sea bed
Opis:
This paper presents results of a study on the relationship between features of side scan sonar acoustic imagery of zones with active bedforms and geomorphologic seafloor characteristics. Acoustic measurements were conducted in Hornsund, a Svalbard fjord representing a periglacial environment with great intensity of morphodynamic processes and rapidly progressing changes of tidewater glaciers. Due to the intensity of these processes, Arctic fjords are the most promising areas to study the effects of climate change on the ecosystem. Acoustic identification of sedimentary structures and morphological forms created by currents and iceberg transport of glacier sediment away from the ice margin was performed. The spectral and fractal features of the recorded signals were analysed. The proposed analysis scheme allows identification of the morphodynamic active zones in the changing Arctic fjord environments. Measurements of acoustical features of seafloor surface were made during the 2006 Arctic cruise of r/v Oceania.
Źródło:
Hydroacoustics; 2008, 11; 401-411
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Applications of the Huang – Hilbert transformation in non-invasive research of the seabed in the Southern Baltic Sea
Autorzy:
Grabowski, M.
Tęgowski, J.
Nowak, J.
Powiązania:
https://bibliotekanauki.pl/articles/331918.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
This article aims at describing methods for extracting the Quaternary facies and detection of a buried pipeline at the bottom with the Huang – Hilbert transformation (HHT) based on acoustic data recorded by the sub-bottom profiler (SBP). The aforementioned transformation allows a study of nonlinear and/or non-stationary phenomena. A good example of this type of problem is the propagation and reflection of acoustic waves in water and the geological formations occurring beneath the surface of the seabed, as well as their scattering on objects at the bottom. The area in which research has been executed was the southern Baltic Sea, specifically the Outer Puck Bay for Quaternary facies and the stretch north from Władysławowo, for the pipeline. On the basis of the processed data with the HHT, Quaternary facies and the pipeline were determined and identified.
Źródło:
Hydroacoustics; 2014, 17; 69-78
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonlinear acoustical methods in the detection of gassy sediments in the gulf of Gdańsk
Autorzy:
Tęgowski, J.
Jakacki, J.
Klusek, Z.
Rudowski, S.
Powiązania:
https://bibliotekanauki.pl/articles/331810.pdf
Data publikacji:
2003
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
nonlinear acoustical methods
gulf of Gdańsk
acoustical signals
gas
Opis:
The application of nonlinear backscattering of acoustical signals in detection of gas bubbles in subsurface layer of sediment of the Gulf of Gdansk is presented. Gas bubbles concentration was estimated assuming that nonlinear scattering in soft sediments is similar as in water. Summary, difference and double harmonics generated only by gas bubbles were recorded and used for bubble density estimation. Comparisons of the concentrations received from different nonlinear components show generally agreement in calculated bubble density distributions, although values of densities acquired from almost identical volumes in a single transmission differ.
Źródło:
Hydroacoustics; 2003, 6; 151-158
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Novel approach to bottom scattering using a narrow acoustic beam
Autorzy:
Zieliński, A.
Tegowski, J.
Lubniewski, Z.
Demkowicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/332113.pdf
Data publikacji:
2004
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The acoustic response of the ocean bottom to a probing pulse is a complex and complicated process. This process is influenced by with the form of an acoustic transmitting/receiving beam and by the physical processes involved in sound scattering from the surface and the volume of the ocean bottom. The complexities of these phenomena often obscure an intuitive understanding of the underlying principles of echo formation and its reception. In this paper, we propose a simplistic model for this complex process using filter theory. The bottom is represented as a surface reflector with an acoustic wave front sweeping over it with time-varying velocity. The impulse response of a smooth flat bottom is characteristic of a low pass-filter that will greatly attenuate the impinging high frequency pulse. On the other hand, bottom undulations will modulate the reflected signal such that it can be represented by the impulse response of a band-pass filter. The received echo can be represented as the response of such filter to a high frequency pulse. The characteristics and amplitude of the echo are dependent on frequency spectrum overlap between the transmitted pulse spectrum and the filter frequency response. In the paper, we discuss several cases of interest with the intent to provide a solid intuitive understanding of the echo formation from the system point of view.
Źródło:
Hydroacoustics; 2004, 7; 253-258
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acoustic estimation of macrophytes in the Hornsund Fjord (The Svalbard Archipelago)
Autorzy:
Kruss, A.
Tęgowski, J.
Wiktor, J.
Tatarek, A.
Powiązania:
https://bibliotekanauki.pl/articles/332372.pdf
Data publikacji:
2006
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
In this paper we examine the use of side scan sonar for estimation and spatial distribution of macrophytes in Arctic conditions. Acoustic observation were verified by video recordings and biological samplings. Single beam echosounder was also used. The Hornsund Fjord represents a periglacial environment with great diversity of morphodynamic processes and sensitivity for global warming changes so it is one of the most promising areas to research the influence of the climate’s impact on ecosystem. Side scan sonar is a very effective and economic tool for mapping marine vegetation on the seafloor but interpretation of data still causes many problems especially in the specific conditions of the Arctic fjords (underwater rocks, postglacial sediments, steep slopes). We have created segmentation and classification algorithm based on the two-dimensional discrete wavelet decomposition of echo signals and fuzzy c-means data clustering. The algorithm was verified using biological data.
Źródło:
Hydroacoustics; 2006, 9; 89-96
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Principal component and cluster analysis for determining diversification of bottom morphology based on bathymetric profiles from Brepollen (Hornsund, Spitsbergen)
Autorzy:
Moskalik, T.
Tegowski, J.
Grabowiecki, P.
Zulichowska, M.
Powiązania:
https://bibliotekanauki.pl/articles/47566.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Oceanologii PAN
Tematy:
principal component
cluster analysis
bottom morphology
diversification
bathymetry
Hornsund
Spitsbergen
post-glacial region
Źródło:
Oceanologia; 2014, 56, 1
0078-3234
Pojawia się w:
Oceanologia
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelling multistatic of target detection
Autorzy:
Klusek, Z.
Elminowicz, A.
Tęgowski, J.
Szczucka, J.
Dragan, A.
Powiązania:
https://bibliotekanauki.pl/articles/331565.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
Gdansk Gulf
chirp signals
hydroacoustic
Opis:
The paper presents a numerical approach to modelling the detection of underwater targets with a bi- or multistatic active sonar systems in the shallow water areas using different waveform signals. The results of the numerical modelling of surface, bubble clouds and bottom reverberation for CW and using up and down time-varying instantaneous frequency of chirp signals are presented. Some suggestions are made on the basis of the development and practicality for the shallow sea modeling techniques and approaches to existing sonar models. The paper reports the literature of the model components required for active sonar modelling for different propagation conditions. Some examples of scattering of CW and chirp source signals at bubble clouds and corrugated surfaces, and coherence are given. Active propagation and the system performance are surveyed and modelled adaptable to the specific environmental condition of the shallow sea area of the Gdansk Gulf.
Źródło:
Hydroacoustics; 2008, 11; 131-138
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 18

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