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    Observationally constrained modeling of sound in curved ocean internal waves: Examination of deep ducting and surface ducting at short range (2011)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2011. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 130 (2011): 1173-1187, doi:10.1121/1.3605565.
    Description: A study of 400 Hz sound focusing and ducting effects in a packet of curved nonlinear internal waves in shallow water is presented. Sound propagation roughly along the crests of the waves is simulated with a three-dimensional parabolic equation computational code, and the results are compared to measured propagation along fixed 3 and 6 km source/receiver paths. The measurements were made on the shelf of the South China Sea northeast of Tung-Sha Island. Construction of the time-varying three-dimensional sound-speed fields used in the modeling simulations was guided by environmental data collected concurrently with the acoustic data. Computed three-dimensional propagation results compare well with field observations. The simulations allow identification of time-dependent sound forward scattering and ducting processes within the curved internal gravity waves. Strong acoustic intensity enhancement was observed during passage of high-amplitude nonlinear waves over the source/receiver paths, and is replicated in the model. The waves were typical of the region (35 m vertical displacement). Two types of ducting are found in the model, which occur asynchronously. One type is three-dimensional modal trapping in deep ducts within the wave crests (shallow thermocline zones). The second type is surface ducting within the wave troughs (deep thermocline zones).
    Description: Grants from the Office of Naval Research funded this work. Use of the vessels Ocean Researcher I and Ocean Researcher II in this experiment was funded by the Taiwan National Science Council.
    Keywords: Acoustic field ; Acoustic focusing ; Acoustic intensity ; Acoustic wave scattering ; Acoustic wave velocity ; Ocean waves ; Oceanographic regions ; Underwater acoustic propagation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Sonar-induced pressure fields in a post-mortem common dolphin (2012)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 1595-1604, doi:10.1121/1.3675005.
    Description: Potential physical effects of sonar transmissions on marine mammals were investigated by measuring pressure fields induced in a 119-kg, 211-cm-long, young adult male common dolphin (Delphinus delphis) cadaver. The specimen was instrumented with tourmaline acoustic pressure gauges used as receiving sensors. Gauge implantation near critical tissues was guided by intraoperative, high-resolution, computerized tomography (CT) scanning. Instrumented structures included the melon, nares, ear, thoracic wall, lungs, epaxial muscle, and lower abdomen. The specimen was suspended from a frame equipped with a standard 50.8-mm-diameter spherical transducer used as the acoustic source and additional receiving sensors to monitor the transmitted and external, scattered field. Following immersion, the transducer transmitted pulsed sinusoidal signals at 5, 7, and 10 kHz. Quantitative internal pressure fields are reported for all cases except those in which the gauge failed or no received signal was detected. A full necropsy was performed immediately after the experiment to examine instrumented areas and all major organs. No lesions attributable to acoustic transmissions were found, consistent with the low source level and source-receiver distances.
    Description: Work supported by NOPP through ONR Grant No. N000140710992. Work at CSI additionally supported by ONR Grant No. N000140811231.
    Keywords: Acoustic radiators ; Acoustic receivers ; Acoustic signal processing ; Acoustic tomography ; Acoustic transducers ; Acoustic wave scattering ; Acoustic wave transmission ; Bioacoustics ; Cellular biophysics ; Computerised tomography ; Ear ; Lung ; Muscle ; Pressure gauges ; Pressure measurement ; Sonar
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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