2019_programme: SOUND SPEED AND ATTENUATION IN WATER-SATURATED SAND-SIZED MATERIALS AT MHZ FREQUENCIES



  • Session: 12. Marine sediment acoustics
    Organiser(s): Ballard Megan , Lee Kevin
  • Lecture: SOUND SPEED AND ATTENUATION IN WATER-SATURATED SAND-SIZED MATERIALS AT MHZ FREQUENCIES [invited]
    Paper ID: 987
    Author(s): Hare Jenna, Hay Alex
    Presenter: Hare Jenna
    Presentation type: oral
    Abstract: Acoustic remote-sensing technologies represent particularly attractive -- potentially breakthrough -- approaches to measuring bedload transport in energetic oceanic conditions because the measurement can be made without disturbing the mobile bed material, or the near-bed flow. The challenge is how to account correctly for multiple scattering in the inversion from backscatter amplitude to particle concentration within the dense bedload layer. This challenge exists because the inversion is non-linear and the predictions of attenuation of sound by existing multiple scattering theories differ by an order of magnitude for the frequencies and particles sizes of interest (MHz frequencies and sand-sized particles). In order to discriminate among multiple scattering theories, transmission loss and sound speed measurements for water-saturated granular materials were made using a pair of broadband, calibrated transducers in the 1 to 2 MHz frequency range. Natural sand and glass beads with median grain sizes ranging from 0.22 mm to 0.40 mm were used. In order to remove air bubbles trapped within the sediment, the samples were boiled under pressure before transferring them to the measurement chamber. The results are compared to existing multiple scattering theory as well as to previous experimental results reported in the literature.
  • Corresponding author: Ms Hare Jenna
    Affiliation: Dalhousie University
    Country: Canada
    e-mail: