Deep water towed array measurements at close range

J Acoust Soc Am. 2013 Oct;134(4):3230-41. doi: 10.1121/1.4818869.

Abstract

During the North Pacific Acoustic Laboratory Philippine Sea 2009 experiment, towed array receptions were made from a towed source as the two ships transited from a separation of several Convergence Zones through a Closest Point of Approach at 3 km. A combination of narrowband tones and broadband pulses were transmitted covering the frequency band 79-535 Hz. The received energy arrives from two general paths-direct path and bottom bounce. Bearing-time records of the narrowband arrivals at times show a 35° spread in the angle of arrival of the bottom bounce energy. Doppler processing of the tones shows significant frequency spread of the bottom bounce energy. Two-dimensional modeling using measured bathymetry, a geoacoustic parameterization based upon the geological record, and measured sound-speed field was performed. Inclusion of the effects of seafloor roughness and surface waves shows that in-plane scattering from rough interfaces can explain much of the observed spread in the arrivals. Evidence of out-of-plane scattering does exist, however, at short ranges. The amount of out-of-plane scattering is best observed in the broadband impulse-beam response analysis, which in-plane surface roughness modeling cannot explain.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acoustics* / instrumentation
  • Doppler Effect
  • Geologic Sediments
  • Models, Theoretical
  • Motion
  • Oceanography / instrumentation
  • Oceanography / methods*
  • Oceans and Seas
  • Scattering, Radiation
  • Seawater*
  • Signal Processing, Computer-Assisted
  • Sound Spectrography
  • Sound*
  • Surface Properties
  • Time Factors
  • Transducers
  • Water Movements