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    Tytuł:
    The role of gas bubbles in the acoustical oceanography
    Autorzy:
    Klusek, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/332115.pdf
    Data publikacji:
    2000
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    The paper below presents different aspects of influence of subsurface bubble population on acoustical environment. The role of bubbles in ambient sea noise emission, reverberation processes and signals transmission is presented. The attention has been devoted to specific properties of the Baltic Sea water and its influence on bubble population.
    Źródło:
    Hydroacoustics; 2000, 3; 91-98
    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:
    Towards field measurement of populations of methane gas bubbles in marine sediment: an inversion method required for interpreting two-frequency insonification data from sediment containing gas bubbles
    Autorzy:
    Leighton, T.
    Mantouka, A.
    White, P.
    Klusek, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/331678.pdf
    Data publikacji:
    2008
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    methane
    marine sediment
    gas bubbles
    Opis:
    This paper describes a key stage in the process for developing a new device for the measurement of gas bubbles in sediment. The device is designed to measure gas bubble populations within the top 2 m of marine sediments, and has been deployed at inter-tidal sites along the South coast of England. Acoustic techniques are particularly attractive for such purposes because they can be minimally invasive. However they suffer from the limitation that their results can be ambiguous. Therefore it is good practice to deploy more than one acoustic technique at time. The new device does just this, but it is designed with the practical economy that the task is accomplished with the minimum number of transducers. One of the measurement techniques relies on insonifying the sediment with two frequencies. This paper outlines how the bubble size distribution is inferred through inversion of the signals detected when two frequencies are projected into the sediment. The high attenuation of the sediment makes this interpretation far more difficult that it would be in water. This paper outlines these difficulties and describes how they can be overcome.
    Źródło:
    Hydroacoustics; 2008, 11; 203-224
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the concentrations of gas bubbles measured acoustically in the Baltic Sea - wind and time dependences
    Autorzy:
    Klusek, Z.
    Jakacki, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/331914.pdf
    Data publikacji:
    1997
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    A linear and nonlinear two-frequency acoustical technique has been used to make in situ measurements of gas bubbles profiles in the Baltic Sea. At three pairs of frequencies namely 30/35, 57/63 and 110/115 kHz spectral components of linear and nonlinear backscattered signal were extracted and their wind and depth dependences have been calculated. Preliminary results of nonlinear backscattering from the subsurface layer of gas bubbles in different hydrological conditions are presented.
    Źródło:
    Hydroacoustics; 1997, 1; 103-108
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The acoustic excitation of newly-formed bubbles
    Autorzy:
    Deane, G.
    Czerski, H.
    Stokes, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/331506.pdf
    Data publikacji:
    2008
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    gas bubbles
    hydroacoustics
    natural frequency
    Opis:
    Gas bubbles in water act as oscillators with a natural frequency inversely proportional to their radius and a quality factor determined by thermal, radiation, and viscous losses. Newly-formed gas bubbles are excited into breathing mode oscillations immediately after creation, causing them to radiate a pulse of sound. Although the linear dynamics of spherical gas bubbles are well-understood, the mechanism driving the sound production has not been unambiguously identified. Using bubbles released from a nozzle as a model system, it can be shown that sound production is consistant with the rapid change in volume associated with the collapse of an air neck formed immediately after bubble pinch-off. The model is able to adequately describe the production of sound by bubbles released from a nozzle, and can also explain some of the acoustic properties of bubbles fragmenting in fluid turbulence. Laboratory experiments and model calculations of the mechanism are presented. [Work supported by ONR and NSF].
    Źródło:
    Hydroacoustics; 2008, 11; 71-78
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-5 z 5

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