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  • Comparative Studies. Non-European Languages/Literatures  (5)
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  • Comparative Studies. Non-European Languages/Literatures  (5)
RVK
  • 1
    Online Resource
    Online Resource
    Measurement of oceanic bubble populations using broadband acoustics
    Acoustical Society of America (ASA) ; 2000
    In:  The Journal of the Acoustical Society of America Vol. 108, No. 5_Supplement ( 2000-11-01), p. 2491-2491
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 108, No. 5_Supplement ( 2000-11-01), p. 2491-2491
    Abstract: The size distribution of bubbles in the ocean will evolve with a number of different temporal and spatial scales as a result of both the physics which govern their formation (breaking wind waves, breaking waves in the surf zone, or ship wakes) and the physical processes which control their lifetimes: turbulent mixing, bubble rise speed, and gas dissolution. A broadband acoustic bubble sizing technique that is suitable for deployment in the rigors of the ocean environment has been developed and deployed on a number of occasions to study the physics of the bubble field and their implications to underwater sound propagation (Terrill and Melville, 2000). The technique is based upon inversions of direct acoustic attenuation and sound-speed measurements at frequencies ranging from approximately 2–200 kHz using broadband pulse transmissions at ping rates up to 25 Hz across short path lengths of O (0.1–1) m. The accuracy of the measured bubble size distributions has been confirmed with both internal consistency checks based on the complex dispersion relationship as well as laboratory comparisons with independent optical techniques. A review of the development of the bubble sizing instrumentation will be presented and results from a number of different field deployments discussed.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4743196
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2000
    detail.hit.zdb_id: 1461063-2
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Time-varying broadband interference patterns in the acoustic field during a shallow water, fixed-fixed experiment
    Acoustical Society of America (ASA) ; 2001
    In:  The Journal of the Acoustical Society of America Vol. 109, No. 5_Supplement ( 2001-05-01), p. 2420-2420
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 109, No. 5_Supplement ( 2001-05-01), p. 2420-2420
    Abstract: During a joint experiment between the Marine Physical Laboratory and the Applied Research Lab, Penn State University in Fall, 2000, continuous-broadband signals in the 100–400 Hz band were transmitted from a moored source to a large-aperture horizontal hydrophone array on the ocean bottom in 175-m water. Spectrograms over a 24-hour period were created from the data from several array elements. These long-duration spectrograms show sinuous interference patterns formed by the regions of modal constructive interference that can be easily traced throughout the entire 24-hour period. The time dependence of the amplitude and center frequency of these individual serpentine structures are correlated with variations in environmental conditions. In particular, their frequency-meandering nature is associated both with tidally driven changes in water depth and the watch circle of the moored source. Temporal oscillations in their amplitude occur with the same periods as those of internal waves. Abrupt jumps in their frequency content occur at the same time as rapid thickening of the upper mixed layer. A simple analytical model is used to predict many of these characteristics. [Work supported by ONR, Code 321US.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4744565
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2001
    detail.hit.zdb_id: 1461063-2
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Bubbles and surf zone oceanography
    Acoustical Society of America (ASA) ; 1998
    In:  The Journal of the Acoustical Society of America Vol. 103, No. 5_Supplement ( 1998-05-01), p. 2828-2829
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 103, No. 5_Supplement ( 1998-05-01), p. 2828-2829
    Abstract: Breaking waves in the surf zone entrain high-density clouds of bubbles which are subsequently transported offshore via rip currents and turbulent diffusion. The presence of the bubbles presents a complex problem for acousticians interested in the propagation of natural and man-made sound in this shallow water regime. To investigate the acoustical properties of this area, a multi-investigator experiment was performed near the Scripps Pier in March 1997. A broadband acoustic technique, developed at the Marine Physical Laboratory, was deployed in a four-channel configuration in water of 6-m depth. Each channel of the system allows the determination of the bubble size distributions at a discrete depth via inversion of the measured sound speed and attenuation. Analysis of the data shows high concentrations of bubbles advecting offshore via rip currents, resulting in acoustic attenuations ranging from O(1)–O(100) dB/m. Vertical gradients were observed in the bubble concentrations. Simultaneous measurements of the wind, waves, and currents provide a synoptic view of the overlying oceanography during the course of the experiment. Results of the experiment will be discussed in the context of the transport of surf-generated bubbles through the measurement site.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.421942
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1998
    detail.hit.zdb_id: 1461063-2
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  • 4
    Online Resource
    Online Resource
    A broadband acoustic technique for measuring bubble size distributions
    Acoustical Society of America (ASA) ; 1996
    In:  The Journal of the Acoustical Society of America Vol. 100, No. 4_Supplement ( 1996-10-01), p. 2840-2841
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 100, No. 4_Supplement ( 1996-10-01), p. 2840-2841
    Abstract: The development of a broadband sound velocimeter allows the simultaneous measurement of sound speed and attenuation over a wide range of frequencies, providing insight into the dispersive characteristics of a bubbly medium. The velocimeter measures the dispersion of a broadband acoustic pulse containing power over frequencies ranging from 2 to 140 kHz across a fixed pathlength. The resulting data are inverted using a simple inversion scheme to arrive at bubble size distributions over a range of radii extending from 20 to 1600 μm. A large wind wave channel located at the Hydraulics Laboratory-S.I.O. provides an ideal location for testing and calibration of the system. Filled with seawater, the channel can generate O(1 m) breaking waves, providing bubble size distributions similar to those found in the field. Results of the lab measurements and comparisons of inverted bubble size distributions with an independent optical bubble sizing technique will be discussed. Preliminary results of a near-shore deployment of the system will be presented, emphasizing results of the data inversions in context of previously reported bubble size distributions. [Work supported by NSF and ONR.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.416721
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1996
    detail.hit.zdb_id: 1461063-2
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  • 5
    Online Resource
    Online Resource
    Sound-speed measurements in the surface wave zone during ASREX
    Acoustical Society of America (ASA) ; 1996
    In:  The Journal of the Acoustical Society of America Vol. 100, No. 4_Supplement ( 1996-10-01), p. 2807-2807
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 100, No. 4_Supplement ( 1996-10-01), p. 2807-2807
    Abstract: Wave breaking at the ocean–atmosphere interface injects air into the surface waters in the form of bubbles, altering the acoustical properties of the water. In situ sound-speed measurements at 3, 5, and 10 kHz were obtained in this dynamic near-surface layer using a moored sound-speed profiling buoy. The buoy was deployed in the North Atlantic during the winter of 1993-94 and obtained more than 40 days of data as part of the ASREX experiment. The record spans several storms, many with winds and significant wave heights in excess of 15 m/s and 7 m, respectively. Surface sound-speed measurements made in the first 7 m of the water column reveal large sound-speed reductions that are a result of air injection due to breaking waves. The data reveal the variable nature of the surface layer, both in short time scales O(seconds-minutes) that result from individual air-injection events, as well as longer time scales O(days) from one storm to another. Results of correlating the sound-speed field with environmental conditions will be discussed. The relationship between low-frequency, nondispersive sound speed and void fraction of air in water [A. B. Wood, A Textbook of Sound(1941)] make the resulting data useful for both oceanographers and acousticians. [Work supported by ONR.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.416560
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1996
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
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    Online Resource
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