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  • Comparative Studies. Non-European Languages/Literatures  (6)
  • 1
    Online Resource
    Online Resource
    On the analysis of the time spreading of sound diffusers
    Acoustical Society of America (ASA) ; 2008
    In:  The Journal of the Acoustical Society of America Vol. 123, No. 5_Supplement ( 2008-05-01), p. 3759-3759
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 123, No. 5_Supplement ( 2008-05-01), p. 3759-3759
    Abstract: Since the invention of sound diffusers three decades ago a substantial effort has been made to predict the acoustic behaviour of these structures. BEM methods are well established for this purpose after a systematic comparison between simulations and experimental data. Volumetric methods such as finite element methods (FEM) or the finite difference time domain method (FDTD) are not often used, due to their large computational cost. However, near to far field transformations (NFFT) can overcome that problem. Recently some of the authors have shown that the FDTD method is a useful technique to analyse the time domain signature of sound diffusers. In this paper a careful analysis of the performance of diffusers in the time domain (“time spreading”) are reported, opening a new field of research.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.2935339
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2008
    detail.hit.zdb_id: 1461063-2
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  • 2
    Online Resource
    Online Resource
    Population density imagery of migrating herring shoals by ocean acoustic waveguide remote sensing.
    Acoustical Society of America (ASA) ; 2009
    In:  The Journal of the Acoustical Society of America Vol. 126, No. 4_Supplement ( 2009-10-01), p. 2231-2231
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 126, No. 4_Supplement ( 2009-10-01), p. 2231-2231
    Abstract: Ocean acoustic waveguide remote sensing (OAWRS) is a bistatic multibeam wide area sonar system that enables unaliased monitoring of fish populations over ecosystem scales. This allows us to quantify the formation processes of vast shoals of Atlantic herring (Clupea harengus) containing hundreds of millions of individuals, imaged during the Autumn 2006 spawning season. Areal population density estimation requires calibration of the low-frequency target strength of an individual shoaling herring. This is estimated from experimental data acquired simultaneously at multiple frequencies in the 300–1200-Hz range using (1) the OAWRS system, (2) areal population density calibration with several conventional fish finding sonar systems (CFFS), (3) fish length distributions obtained from trawl samples, and (4) local low-frequency transmission loss measurements. High spatial-temporal co-registration was found between shoals imaged by OAWRS and concurrent CFFS line transects, which also provided fish depth distributions. The mean scattering cross-section of an individual shoaling herring is found to exhibit a strong dependence on frequency in the OAWRS range, which is consistent with resonant scattering from an air-filled swimbladder. We show that a rapid transition from disordered to highly synchronized behavior occurs as the herring population density reaches a critical value, after which an organized group migration occurs.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.3249166
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2009
    detail.hit.zdb_id: 1461063-2
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  • 3
    Online Resource
    Online Resource
    Low-frequency target strength and abundance of shoaling Atlantic herring ( Clupea harengus ) in the Gulf of Maine during the Ocean Acoustic Waveguide Remote Sensing 2006 Experiment
    Acoustical Society of America (ASA) ; 2010
    In:  The Journal of the Acoustical Society of America Vol. 127, No. 1 ( 2010-01-01), p. 104-123
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 127, No. 1 ( 2010-01-01), p. 104-123
    Abstract: The low-frequency target strength of shoaling Atlantic herring (Clupea harengus) in the Gulf of Maine during Autumn 2006 spawning season is estimated from experimental data acquired simultaneously at multiple frequencies in the 300–1200Hz range using (1) a low-frequency ocean acoustic waveguide remote sensing (OAWRS) system, (2) areal population density calibration with several conventional fish finding sonar (CFFS) systems, and (3) low-frequency transmission loss measurements. The OAWRS system’s instantaneous imaging diameter of 100km and regular updating enabled unaliased monitoring of fish populations over ecosystem scales including shoals of Atlantic herring containing hundreds of millions of individuals, as confirmed by concurrent trawl and CFFS sampling. High spatial-temporal coregistration was found between herring shoals imaged by OAWRS and concurrent CFFS line-transects, which also provided fish depth distributions. The mean scattering cross-section of an individual shoaling herring is found to consistently exhibit a strong, roughly 20dB/octave roll-off with decreasing frequency in the range of the OAWRS survey over all days of the roughly 2-week experiment, consistent with the steep roll-offs expected for sub-resonance scattering from fish with air-filled swimbladders.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.3268595
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2010
    detail.hit.zdb_id: 1461063-2
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  • 4
    Online Resource
    Online Resource
    Atlantic herring low-frequency target strength and abundance estimation: Ocean acoustic waveguide remote sensing (OAWRS) 2006 Experiment in the Gulf of Maine.
    Acoustical Society of America (ASA) ; 2008
    In:  The Journal of the Acoustical Society of America Vol. 124, No. 4_Supplement ( 2008-10-01), p. 2586-2586
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 124, No. 4_Supplement ( 2008-10-01), p. 2586-2586
    Abstract: The mean low-frequency target strength (TS) of spawning Atlantic herring populations in the Gulf of Maine is estimated from the experimental data acquired during September–October 2006 near the northern flank of Georges Bank. A low-frequency OAWRS system with an instantaneous imaging diameter of 100 km was deployed to provide spatially unaliased imaging of fish populations over wide areas. The OAWRS system’s scattering strength measurements are calibrated with areal fish population density estimates obtained from concurrent localized line-transect measurements with several conventional fish finding sonars (CFFSs). Trawl sampling at selected locations enables the identification of the imaged species. The mean TS estimates of herring individuals exhibits significant variation over OAWRS operating frequency range, in accordance with the results from a resonant scattering model for swimbladder-bearing fish. The neutral buoyancy depth of herring and the species composition in the imaged population is inferred by comparing the measured TS with those derived from the model. Our analysis indicates that the herring population has a neutral buoyancy depth of between 70 and 90 m and is therefore negatively buoyant between 120 and 180 m water depth at which it is commonly found. The herring populations instantaneously imaged with OAWRS often exceeds 200×106, of which over 150×106 individuals can be organized into a large shoal.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4783201
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2008
    detail.hit.zdb_id: 1461063-2
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  • 5
    Online Resource
    Online Resource
    Spawning behavior and spatial distribution of Atlantic herring on Georges Bank revealed by ocean acoustics waveguide remote sensing
    Acoustical Society of America (ASA) ; 2007
    In:  The Journal of the Acoustical Society of America Vol. 122, No. 5_Supplement ( 2007-11-01), p. 3003-3003
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 122, No. 5_Supplement ( 2007-11-01), p. 3003-3003
    Abstract: An ocean acoustics waveguide remote sensing (OAWRS) system was deployed in the Gulf of Maine, near Georges Bank to image Atlantic herring and other fish population from September–October 2006. OAWRS provides spatially unaliased imaging of herring over wide areas, spannning over 100 km diam. Migration and spawning behavior of Atlantic herring were observed using OAWRS over several diurnal periods, including massive movements on and off the bank to spawn. Measurements made simultaneously with a conventional fish-finding echosounder (CFFS) and a multibeam sonar provide the depth distribution and local 3-D morphology, respectively, of the herring schools in the water column. Concurrent trawl surveys provide identification of the fish species. Measurements made by OAWRS and CFFS systems are highly correlated. Examples will be provided of the co-registration between the two systems over a one-week period. Calibration of the OAWRS system using CFFS estimates of fish population densities, along with a full-field scattering model that takes into account both coherent and incoherent scattering from a fish group, is discussed. Resonance scattering behavior of herring is observed in the OAWRS system with significant changes in scattering amplitude over the 300 Hz to 1.5 kHz frequency range of the OAWRS system.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.2942723
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2007
    detail.hit.zdb_id: 1461063-2
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    Online Resource
  • 6
    Online Resource
    Online Resource
    Spawning Behaviour and Spatial Distribution of Atlantic Herring on Georges Bank Revealed by Ocean Acoustics Waveguide Remote Sensing
    Acoustical Society of America (ASA) ; 2008
    In:  The Journal of the Acoustical Society of America Vol. 123, No. 5_Supplement ( 2008-05-01), p. 3103-3103
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 123, No. 5_Supplement ( 2008-05-01), p. 3103-3103
    Abstract: An ocean acoustics waveguide remote sensing (OAWRS) system was deployed in the Gulf of Maine, near Georges Bank to image Atlantic herring and other fish populations from Sep-Oct 2006. OAWRS provides spatially unaliased imaging of herring over wide areas, spannning over 100 km diameter. Migration and spawning behaviour of Atlantic herring was observed using OAWRS over several diurnal periods, including massive movements on and off the bank to spawn. Measurements made simultaneously with a conventional fish-finding echosounder (CFFS) and a multibeam sonar provide the depth distribution and local 3D morphology respectively of the herring schools in the water column. Concurrent trawl surveys provide identification of the fish species. Measurements mades by OAWRS and CFFS systems are highly correlated. Examples will be provided of the co-registration between the two systems over a one week period. Calibration of the OAWRS system using CFFS estimates of fish population densities along with a full-field scattering model that takes into account both coherent and incoherent scattering from a fish group is discussed. The fish swimbladder is modelled as a spheroidal bubble. Resonance scattering behaviour of herring is observed in the OAWRS system with significant changes in scattering amplitude over the 300 Hz to 1.5 kHz frequency range of the OAWRS system.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.2932969
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2008
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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