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    Wyświetlanie 1-13 z 13
    Tytuł:
    Detekcja źródeł szumów podwodnych z wykorzystaniem falki Malvara
    The detection of underwater noise sources using Malvar wavelet
    Autorzy:
    Jerzman, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/151398.pdf
    Data publikacji:
    2007
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    wielorozdzielcza analiza falkowa
    falka Malvara
    estymacja wielowymiarowej funkcji gęstości prawdopodobieństwa
    szumy podwodne
    multiresolution wavelet analysis
    Malvar wavelet
    underwater noise
    Opis:
    W referacie zamieszczono wyniki badań modelu detekcji źródeł szumów podwodnych, bazującego na estymacji funkcji gęstości prawdopodobieństwa rozkładu energii w pasmach dekompozycji falkowej sygnałów pomiarowych. Celem badań było ilościowe porównanie wyników detekcji zaburzeń powodowanych przez płetwonurka w środowisku podwodnym, z wykorzystaniem w procesie przetwarzania sygnałów pomiarowych falek Daubechies oraz Malvara. Wyniki badań wskazują, że wykorzystanie lokalnych transformacji Malvara pozwala na bardziej efektywne wykorzystanie zastosowanej metody detekcji.
    The paper presents the results of the research on the model of detection of the underwater noise sources. This model is based on the multivariate kernel density estimate of the energy of multidimensional wavelet coefficients. The conventional method of signal decomposition using Daubechies wavelet is compared with the algorithm which implements Malvar wavelet. This type of decomposition was adapted to the method of detection of underwater disturbances coming from unnatural sources. The outcome of theoretical considerations was supported by the figures presenting the results of simulation experiments on the real noise signals. The aim of the research was the numerical comparison and the evaluation of the effectiveness of the detection of signals generated by the diver using the Malvar wavelet or the standard Daubechies wavelet. The specific and distinct character of Malvar wavelet implementation strongly affects the method of detection thus the analysis of the results of the modification seems to be interesting. The research proved that the exploitation of local Malvar transforms reduces the number of computations, minimizes the detection result. Moreover, it enables greater flexibility as far as the parameter selection is concerned.
    Źródło:
    Pomiary Automatyka Kontrola; 2007, R. 53, nr 9, 9; 48-51
    0032-4140
    Pojawia się w:
    Pomiary Automatyka Kontrola
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Sound and vibration analysis for 70 m supply vessel in aspect of underwater noise reduction
    Autorzy:
    Weryk, M.
    Kusmirek-Ochrymiuk, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/331657.pdf
    Data publikacji:
    2008
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    underwater noise reduction
    hydroacoustics
    vessel
    Opis:
    The underwater noise and on-board noise measurement analysis, for 70 m supply ship, are presented in the paper, as well as the noise data for main machinery installed on-board. The results were completed by vibration measurements, then comparative analysis and identification of main sources of sound were executed. The main aim for this project was to analyse noise propagation and identify main noise excitation components resulting in underwater noise propagation. Some preliminary proposals of underwater noise reduction are put forward in the paper.
    Źródło:
    Hydroacoustics; 2008, 11; 431-440
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ships underwater noise measurements using sound intensity method
    Autorzy:
    Gloza, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/332552.pdf
    Data publikacji:
    2009
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    underwater noise
    ships
    sound intensity method
    Opis:
    Ship noise is a most important part of the field of underwater acoustics. Its reduction and monitoring is an important aspect in the performance of underwater acoustic systems and in the habitability of the vessel for the crew and passengers. In naval operations the noise radiated by a ship is also dominant source of information for underwater sonar systems. Sound intensity is the vector quantity which informs us about the sound power flux, the position and the direction of the sound source. The probe tracks the position of source and at the same time, measures the component of sound-intensity vector. Generally only one component of vector sound intensity was measured, perpendicular to a given measurement surface. The sound intensity of a moving source includes effects such as flow noise that are not present when the source is stationary. The accuracy of measuring acoustic intensity using two closely spaced hydrophones by correcting the phase mismatch error by measuring the transfer function between the two detector systems was examined. The two measuring hydrophone instrumentation systems were earlier calibrated. Our results have been obtained using digital methods, where was used PULSE measuring system.
    Źródło:
    Hydroacoustics; 2009, 12; 53-60
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Underwater Noise Generated by a Small Ship in the Shallow Sea
    Autorzy:
    Grelowska, G.
    Kozaczka, E.
    Kozaczka, S.
    Szymczak, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/177360.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    signal processing
    sound propagation
    underwater ship noise
    propagation in the shallow sea
    Opis:
    Study of the sea noise has been a subject of interest for many years. The first works in this scope were published at the turn of the twentieth century by Knudsen (Knudsen et al., 1948) and G. Wenz (Wenz, 1962). Disturbances called “shipping noise” are one of the important components of the sea noise. In this work the results of an experimental research of underwater noise produced by a small ship of a classic propulsion are presented. A linear receiving antenna composed of two orthogonal components was used in the investigation. Identification of the main sources of acoustic waves related with the ship was achieved. In addition, the intensity of the wave was measured. The research was performed in conditions of the shallow sea.
    Źródło:
    Archives of Acoustics; 2013, 38, 3; 351-356
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Prediction of Tonal Underwater Noise Pattern from Cavitating Propellers with Special Attention to Ice Cover Effects
    Autorzy:
    Streckwall, H.
    Bretschneider, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/259712.pdf
    Data publikacji:
    2014
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    cavitation
    underwater noise
    ice-covered areas
    Opis:
    To predict underwater noise spectra associated to regular occurrence of propeller cavitation we have extended an existing method [1] (used for the prediction of fluctuating hull pressures) to become applicable for effects that are linked to a finite speed of sound. In [2] an intermediate approach was realized where (besides the hull) far field boundaries were introduced but the incompressible flow assumption was kept. However compressibility effects become noticeable in the far field, which may be judged to start at some 2-3 propeller-diameters distance from the centre of the cavitation events, if we confine to emissions at 1st- 4th blade frequency. It was a logical continuation of our former efforts to realize a compressible flow model and integrate the propeller as a noise source. Having increased the functionality of our approach by referencing the speed of sound, the precision of the method was also somehow reduced. In our former approach, like in comparable approaches (see for instance [3] and [4]), the singularity system generating the near field propeller induced pressures involved various sources and vortices distributed on the propeller blades. With our current compressible approach this complexity was dropped, as a single point source substitutes the cavitating propeller. Such a simplification correlates with the assumption, that the monopole character of a noise source is decisive for the far field noise levels. In this contribution we outline the steps characterizing the procedure for predicting tonal underwater noise from cavitating propellers. In the first step a Vortex Lattice Method (VLM) is used to access the cavitation pattern on the propeller with special focus on the cavity volume attached to one blade. The second step accumulates the distributed cavities to establish a fluctuating point source of equivalent far field noise characteristic. As relevant limits the hull, the free surface, the sea bottom and an ice cover are introduced. Using finally a Boundary Element Method (BEM) approach the relevant noise characteristics are derived, accounting for external boundaries and for the finite speed of sound. The results provided here are focused on a comparative treatment of different scenarios, mainly addressing ice cover effects at finite the water depth.
    Źródło:
    Polish Maritime Research; 2014, 4; 35-40
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Selected characteristics of shipping noise at the fairway of the Gdynia Harbour
    Autorzy:
    Klusek, Z.
    Szczucka, J.
    Mróz, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/332266.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    Baltic Sea
    anthropogenic underwater noise
    shipping
    Opis:
    The presented work aims to evaluate the possible impact of shipping noise on the marine fauna in the vicinity of the Gdynia Harbour. Measurements were performed in the area at the distance of 0.2 NM to the fairway. For this purpose, statistics of Sound Pressure Level (SPL), Sound Exposure Level (SEL), and Power Spectral Density (PSD) were evaluated. Some specific changes of the ambient and shipping noise spectra are given in examples.
    Źródło:
    Hydroacoustics; 2015, 18; 203-214
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Signal conditioning for examination of shallow-water acoustic noise correlation properties
    Autorzy:
    Rudnicki, M.
    Marszal, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/331724.pdf
    Data publikacji:
    2016
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    underwater acoustics
    ambient noise
    noise envelope
    tetrahedral antenna
    Opis:
    The 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 noise. Quantitative estimation of the correlation properties of acoustic noise enables an accurate determination of detection conditions. This will verify the validity of certain commonly used simplified models in simulations of hydroacoustic systems. The article presents how the measurement system was constructed, and the structure of files for storing measurement data. It describes the processing algorithm developed for the measured signal conditioning. Research results are presented and discussed.
    Źródło:
    Hydroacoustics; 2016, 19; 335-340
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Impact of salinity on the underwater noise generated by small scale air entrainment events
    Autorzy:
    Szuszkiewicz, J.
    Klusek, Z.
    Gorska, N.
    Powiązania:
    https://bibliotekanauki.pl/articles/332616.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    underwater noise
    air entrainment
    bubbles
    bubble clusters
    Opis:
    Some part of the energy released in the wave breaking process is transformed into the energy of the noise. This sound depends on the water properties, however, there is a lack of reliable data concerning the underwater noise generated by less energetic events. The aim of this study was to understand the impact of salinity on the underwater noise produced during small scale air entrainment events, typical for low wind speed conditions. The tipping trough experiment was performed in a small tank to generate the small scale air injections. Four, linearly placed hydrophones HTI-96-MIN were used to record the acoustic noise accompanying this phenomenon. The bubble plume development, and underwater noise spectra, were compared for salty and fresh water. The potential energy of the modeled events resulted in different spectra, and salinity played an essential role in the emitted underwater noise.
    Źródło:
    Hydroacoustics; 2017, 20; 167-172
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Propagation of ship-generated noise in shallow sea
    Autorzy:
    Kozaczka, E.
    Grelowska, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/259166.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    shallow water acoustics
    propagation of acoustic waves in water layer
    wave modes in shallow sea
    underwater noise produced by ship
    Opis:
    Contamination of sea environment by noise and any energy radiated to water constitutes today a problem to which more and more attention is paid, in view, a.o., of consequences of an impact of these factors onto marine fauna. European Union has introduced a directive by which EU countries are made responsible to undertake efforts aimed at reaching a good envirenmental status of European seas by 2020. A main source of underwater noise is sea transport of any kind. Propagation of underwater acoustic disturbances in the Baltic Sea highly differs from the course of the phenomenon in a deep sea. Model of spherical propagation cannot be applied to this case in view of water environment limitation by seabed and free water surface, i.e. a reduction of the problem to wave propagation in a water layer of the depth comparable with acoustic wave length. This paper is aimed at demonstration of possible assessment of range of acoustic disturbances generated by a ship sailing in shallow sea, by using a method described in the work [13]. The research was made on the basis of results of own measurements of underwater noise produced by ships in the Gdansk Bay area. An important factor which decIdes on a range of underwater disturbances is a kind of seabed sediments. In this paper there are presented results of numerical investigations based on real data dealing with noise produced by a selected floating unit (ship) for selected characteristic spectral components. The simulations were conducted for the shallow sea model of definite physical parameters such as acoustic wave propagation velocity, geometrical dimensions (water depth) and seabed acoustic parameters as well.
    Źródło:
    Polish Maritime Research; 2018, 2; 37-46
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Impact of Spatial Noise Correlation on Bearing Accuracy in DIFAR Systems
    Autorzy:
    Rudnicki, Mariusz
    Marszal, Jacek
    Salamon, Roman
    Powiązania:
    https://bibliotekanauki.pl/articles/1953524.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    underwater noise
    noise correlation
    DIFAR sonobuoys
    bearing accuracy
    Opis:
    DIFAR type underwater passive systems are one of the more commonly used tools for detecting submarines. At the design stage, which usually uses computer simulations, it is necessary to generate acoustic noise of the sea. It has been shown that correlating noise significantly reduces these errors compared to the assumption that noise is uncorrelated. In addition, bearing errors have been shown to be the same in systems with a commonly used antenna containing five hydrophones, as in a system without a central hydrophone, which may be useful in some DIFAR system design solutions.
    Źródło:
    Archives of Acoustics; 2020, 45, 4; 709-720
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Observations on relations between marine aerosol fluxes and surface-generated noise in the Southern Baltic Sea
    Autorzy:
    Markuszewski, P.
    Klusek, Z.
    Nilsson, E.D.
    Petelski, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/2079072.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    marine aerosol
    aerosol flux
    noise measurement
    underwater noise
    sea spray
    hydroacoustic measurement
    meteorological condition
    Baltic Sea
    Opis:
    This study presents the preliminary results of combining underwater acoustic ambient noise measurements with those of in-situ sea spray fluxes (SSF). Hydroacoustic measurements (in the frequency range 80 Hz –12.5 kHz) were made using an underwater noise recording system developed at the Institute of Oceanology of the Polish Academy of Sciences which was then deployed in the southern Baltic Sea. The simultaneous measurements of coarse sea spray fluxes (with particle diameters ranging from 0.5 to 47 µm) were made on board the r/v Oceania using the gradient method. Observations were conducted for the duration of the passage of an atmospheric front that lasted 2.5 days (60 hours of measurements). There were significant differences in the sound pressure level (SPL) and aerosol fluxes observed between the first part of measurements (developing wave state) and the second part (developed waves). Wave parameters, such as peak period, significant wave height, wave age, and mean wave slope acquired from the WAM (WAve Model), were used to investigate the impact of wave field properties on noise and aerosol flux measurements. We observed different behaviours in the power spectrum density (PSD) levels of noise for these parameters depending on the wave state development.
    Źródło:
    Oceanologia; 2020, 62, 4PA; 413-427
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Field Study on Underwater Noise Emitted by Small Tourist Boats. Comparison Between the Use of Electric and Combustion Motors
    Autorzy:
    Yori, Alfio
    Powiązania:
    https://bibliotekanauki.pl/articles/31339825.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    small boat underwater noise
    anthropogenic underwater noise
    electric motor boat
    underwater noise produced by tourist boats
    Opis:
    Small boats, possessing outboard engines, are widely used in tourism and mammal watching within marine protected areas. Noise generated by this type of vessels has the capacity to negatively affect marine fauna, especially marine mammals, which use sound throughout all the phases of their lives. These tourism boats used in mammal watching may use different propulsion systems, such as gas, diesel or electric engines. To characterize underwater noise emitted by this type of vessels becomes relevant not only when assessing the acoustic impact produced by these different propulsion systems over the marine fauna living inside these protected marine areas, but also when determining which one produces the least impact. A comparative study of underwater noise emissions coming from small touristic boats was made in this study. Boats were similar in capacity and functions, although possessing different propulsion systems. Measurements were made on two boats with a 50 Hp internal combustion engine and one 5 Hp electric boat. These boats were selected to be studied because they have practically the same size, possess the same passenger-capacity and are used to make similar jobs and routes inside the protected area where they are operated. The electric boat showed a considerable decrease in underwater noise emissions, especially in low frequencies. This boat will produce a lower accumulated exposition of the fauna to the noise or will allow a closer approach to the observed species. Measurements were made between September 2018 and January 2020
    Źródło:
    Archives of Acoustics; 2023, 48, 3; 347-358
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Impulse Excitation in a Watertight Steel Circular Cylindrical Shell and Influence of Structural Configuration on Underwater Radiated Noise
    Autorzy:
    Wu, Chen-I
    Too, Gee-Pinn
    Wu, Bo-Hsien
    Powiązania:
    https://bibliotekanauki.pl/articles/31339791.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    impulse excitation
    influence of structural configuration
    FEM analysis
    underwater noise radiation characteristics
    Opis:
    This study used experimental measurements and the finite-element method (FEM) simulations to investigate transient underwater radiated noise induced by the impulse excitation of water surrounding a watertight steel-structured circular cylindrical shell submerged in the 176 × 8 × 4 m towing tank. The excitation was caused by dropping an iron block onto a structural bracket in the shell to generate structural vibration. The experimental results were found to be consistent with the FEM results, with the difference between the experimental and simulated sound pressure levels being less than 3 dB. Moreover, it was determined that the structural vibration also generated airborne noise in the cylindrical shell, but this contributed much less than the impulse excitation to the induction of underwater radiated noise. Finally, analysis of the sound field of the underwater noise radiation showed that it was influenced by the wall thickness of the watertight steel cylindrical shell and that of the reinforced bracket seat structure. In particular, the structural reinforcement position proved to be the diffusion breakpoint of the underwater sound radiation. This demonstrates that compared with the studied structure, a thicker and more complex reinforced structure will transmit less or incomplete sound radiation into water.
    Źródło:
    Archives of Acoustics; 2023, 48, 4; 509-521
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-13 z 13

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