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  • Array signal processing  (4)
  • ENERGY PRODUCTION AND CONVERSION
  • Fisheries
  • Industrial Chemistry
  • Inorganic Chemistry
  • Meteorology and Climatology
  • Seismology
  • Acoustical Society of America  (6)
  • 2005-2009  (6)
  • 1980-1984
  • 1955-1959
  • 1950-1954
  • 1
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    Three-dimensional beam pattern of regular sperm whale clicks confirms bent-horn hypothesis (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2005. 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 117 (2005): 1473-1485, doi:10.1121/1.1828501.
    Description: The three-dimensional beam pattern of a sperm whale (Physeter macrocephalus) tagged in the Ligurian Sea was derived using data on regular clicks from the tag and from hydrophones towed behind a ship circling the tagged whale. The tag defined the orientation of the whale, while sightings and beamformer data were used to locate the whale with respect to the ship. The existence of a narrow, forward-directed P1 beam with source levels exceeding 210 dBpeak re: 1 µPa at 1 m is confirmed. A modeled forward-beam pattern, that matches clicks 〉20° off-axis, predicts a directivity index of 26.7 dB and source levels of up to 229 dBpeak re: 1 µPa at 1 m. A broader backward-directed beam is produced by the P0 pulse with source levels near 200 dBpeak re: 1 µPa at 1 m and a directivity index of 7.4 dB. A low-frequency component with source levels near 190 dBpeak re: 1 µPa at 1 m is generated at the onset of the P0 pulse by air resonance. The results support the bent-horn model of sound production in sperm whales. While the sperm whale nose appears primarily adapted to produce an intense forward-directed sonar signal, less-directional click components convey information to conspecifics, and give rise to echoes from the seafloor and the surface, which may be useful for orientation during dives.
    Description: This work was funded by grants from the Office of Naval Research Grants N00014-99-1-0819 and N00014-01-1-0705, and the Packard Foundation.
    Keywords: Bioacoustics ; Biocommunications ; Array signal processing ; Echo ; Hydrophones ; Multidimensional signal processing ; Underwater sound ; Sonar signal processing
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Underwater tunable organ-pipe sound source (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2007. 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 122 (2007): 777-785, doi:10.1121/1.2751268.
    Description: A highly efficient frequency-controlled sound source based on a tunable high-Q underwater acoustic resonator is described. The required spectrum width was achieved by transmitting a linear frequency-modulated signal and simultaneously tuning the resonance frequency, keeping the sound source in resonance at the instantaneous frequency of the signal transmitted. Such sound sources have applications in ocean-acoustic tomography and deep-penetration seismic tomography. Mathematical analysis and numerical simulation show the Helmholtz resonator's ability for instant resonant frequency switching and quick adjustment of its resonant frequency to the instantaneous frequency signal. The concept of a quick frequency adjustment filter is considered. The discussion includes the simplest lumped resonant source as well as the complicated distributed system of a tunable organ pipe. A numerical model of the tunable organ pipe is shown to have a form similar to a transmission line segment. This provides a general form for the principal results, which can be applied to tunable resonators of a different physical nature. The numerical simulation shows that the “state-switched” concept also works in the high-Q tunable organ pipe, and the speed of frequency sweeping in a high-Q tunable organ pipe is analyzed. The simulation results were applied to a projector design for ocean-acoustic tomography.
    Description: The work was supported by ONR.
    Keywords: Acoustic generators ; Underwater sound ; Acoustic resonators ; Oceanographic equipment ; Seismology
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
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    Protocols for calibrating multibeam sonar (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2005. 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 117 (2005): 2013-2027, doi:10.1121/1.1869073.
    Description: Development of protocols for calibrating multibeam sonar by means of the standard-target method is documented. Particular systems used in the development work included three that provide the water-column signals, namely the SIMRAD SM2000/90- and 200-kHz sonars and RESON SeaBat 8101 sonar, with operating frequency of 240 kHz. Two facilities were instrumented specifically for the work: a sea well at the Woods Hole Oceanographic Institution and a large, indoor freshwater tank at the University of New Hampshire. Methods for measuring the transfer characteristics of each sonar, with transducers attached, are described and illustrated with measurement results. The principal results, however, are the protocols themselves. These are elaborated for positioning the target, choosing the receiver gain function, quantifying the system stability, mapping the directionality in the plane of the receiving array and in the plane normal to the central axis, measuring the directionality of individual beams, and measuring the nearfield response. General preparations for calibrating multibeam sonars and a method for measuring the receiver response electronically are outlined. Advantages of multibeam sonar calibration and outstanding problems, such as that of validation of the performance of multibeam sonars as configured for use, are mentioned.
    Description: Support by the National Science Foundation through Award No. OCE-0002664, NOAA through Grant No. NA97OG0241, and the Cooperative Institute for Climate and Ocean Research (CICOR) through NOAA Contract No. NA17RJ1223 is acknowledged.
    Keywords: Sonar detection ; Sonar target recognition ; Underwater sound ; Calibration ; Array signal processing ; Acoustic transducer arrays ; Protocols
    Repository Name: Woods Hole Open Access Server
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  • 4
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    A beamforming video recorder for integrated observations of dolphin behavior and vocalizations (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2005. 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 117 (2005): 1005-1008, doi:10.1121/1.1831284.
    Description: In this Letter we describe a beamforming video recorder consisting of a video camera at the center of a 16 hydrophone array. A broadband frequency-domain beamforming algorithm is used to estimate the azimuth and elevation of each detected sound. These estimates are used to generate a visual cue indicating the location of the sound source within the video recording, which is synchronized to the acoustic data. The system provided accurate results in both lab calibrations and a field test. The system allows researchers to correlate the acoustic and physical behaviors of marine mammals during studies of social interactions.
    Description: This research was funded by NSF Ocean Sciences CAREER award 9733391.
    Keywords: Bioacoustics ; Biocommunications ; Array signal processing ; Acoustic correlation ; Video recording ; Frequency-domain analysis ; Acoustic signal detection ; Underwater sound ; Hydrophones
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Modal processing for acoustic communications in shallow water experiment (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2008. 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 124 (2008): EL177-EL181, doi:10.1121/1.2960954.
    Description: Acoustical array data from the Shallow Water Acoustics experiment was processed to show the feasibility of broadband mode decomposition as a preprocessing method to reduce the effective channel delay spread and concentrate received signal energy in a small number of independent channels. The data were collected by a vertical array designed at the Woods Hole Oceanographic Institution. Phase-shift Keying (PSK) m-sequence modulated signals with different carrier frequencies were transmitted at a distance 19.2 km from the array. Even during a strong internal waves activity a low bit error rate was achieved.
    Description: The research was supported by ONR.
    Keywords: Acoustic arrays ; Acoustic signal processing ; Array signal processing ; Modulation ; Underwater acoustic communication
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Geoacoustic inversion by mode amplitude perturbation (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © Acoustical Society of America, 2008. 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 123 (2008): 667-678, doi:10.1121/1.2821975.
    Description: This paper introduces a perturbative inversion algorithm for determining sea floor acoustic properties, which uses modal amplitudes as input data. Perturbative inverse methods have been used in the past to estimate bottom acoustic properties in sediments, but up to this point these methods have used only the modal eigenvalues as input data. As with previous perturbative inversion methods, the one developed in this paper solves the nonlinear inverse problem using a series of approximate, linear steps. Examples of the method applied to synthetic and experimental data are provided to demonstrate the method's feasibility. Finally, it is shown that modal eigenvalue and amplitude perturbation can be combined into a single inversion algorithm that uses all of the potentially available modal data.
    Description: Funding for the research presented here was provided by the Office of Naval Research, and the WHOI Academic Programs Office.
    Keywords: Geophysical techniques ; Inverse problems ; Sediments ; Seismology
    Repository Name: Woods Hole Open Access Server
    Type: Article
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