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  • IEEE  (2)
  • 1
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © IEEE, 2004. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 29 (2004): 1308-1315, doi:10.1109/JOE.2004.836999.
    Beschreibung: This correspondence presents a preliminary examination of the low frequency ambient noise field measured in the South China Sea component of the Asian Seas International Acoustics Experiment (ASIAEX), concentrating on the frequencies of 50, 100, 200, 400, 800, and 1200 Hz. A two-week-long time series of the noise at these frequencies is examined for structure in both the time and frequency domains. Three features of particular interest in these series are: 1) the noise due to a typhoon, which passed near the experimental site, 2) the weak tidal frequency variability of the noise field, which is probably due to internal tide induced variability in the propagation conditions, and 3) the vertical angle dependence of the noise, particularly as regards the shallow water "noise notch" phenomenon. The acoustic frequency dependence and the vertical dependence of the noise field are also examined over the course of the time series. A simple look at the noise variability statistics is presented. Finally, directions for further analysis are discussed.
    Beschreibung: This work was supported by the U.S. Office of Naval Research under Grants N0001498-1-0413, N00014-00-0931, and N00014-01-0772 and by the NSC of Taiwan under Grant NSC92-2611-E110-004-CCS.
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: 1044180 bytes
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © IEEE, 2004. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 29 (2004): 1231-1248, doi:10.1109/JOE.2004.834681.
    Beschreibung: The inversion of a broad-band "source of opportunity" signal for bottom geoacoustic parameters in the northeastern South China Sea (SCS) is presented, which supplements the towed source and chirp sonar bottom inversions that were performed as part of the Asian Seas International Acoustics Experiment (ASIAEX). This source of opportunity was most likely a "dynamite fishing" signal, which has sufficient low-frequency content (5-500 Hz) to make it complimentary to the somewhat higher frequency J-15-3 towed source (50-260 Hz) signals and the much higher frequency (1-10 kHz) chirp signals. This low frequency content will penetrate deeper into the bottom, thus extending the other inverse results. Localization of the source is discussed, using both a horizontal array for azimuthal steering and the "water wave" part of the pulse arrival for distance estimation. A linear broad-band inverse is performed, and three new variants of the broad-band inverse, based on: 1) the Airy phase; 2) the cutoff frequency; and 3) a range-dependent medium are presented. A multilayer model of the bottom compressional wave speed is obtained, and error estimates for this model are shown, both for the range-independent approximation to the waveguide and for the range-dependent waveguide. Directions for future research are discussed.
    Beschreibung: This work was supported by the Office of Naval Research under Grant N0 001 498-1-0413, Grant N00014-00-0931, and Grant N00014-01-0772 and by the National Science Council, Taiwan, R.O.C. under Grant NSC92-2611-E-002-005-CCS.
    Schlagwort(e): Broadband geoacoustic inversions ; Shallow water acoustics ; South China Sea
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: 1203211 bytes
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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