First trial of multi-wavelength vector sensor: Sediment geoacoustic properties obtained from vessel noise off Senegal

Qun Yan Ren, Jean Pierre Hermand, Jo Randall, Michel Verbanck, Patrice Brehmer

Research output: Chapter in Book/Report/Conference proceedingConference Paper published in Proceedings

Abstract

Fisheries survey ECOAO 13, including the collection of surface sediment samples and acoustic propagation measurements, was carried out off the Senegalese coast in February 2013. The bottom acoustic properties were determined by geoacoustic inversion using the noise of R/V Antea as a noise sound source of opportunity. The vessel moved on a straight course with constant engine speed (1627 RPM) while the generated noise field was recorded by a vector sensor array deployed from a reinforced hull inflatable boat launched from the vessel. The multi-wavelength array, designed and built at EHL, is composed of four pressure sensors with different spacing combinations and two pressure gauges. The inversion approach estimates the bottom geoacoustic properties from observation of range-dependent features of vertical impedance at multiple frequencies and optimization based on a genetic algorithm. As compared to our previous two-element array, deployed offshore Amazon, the newly designed array provides more comprehensive observables and therefore more reliable geoacoustic inversion results. For this first trial, the vertical impedance data at the spectral lines of 140 Hz, 280 Hz and 321 Hz were extracted from pairs of adjacent array elements and jointly processed. The bottom compression speed (1640 m/s) and density (1.96 g/cm3) deduced from the posterior probability density functions suggest a sandy seabed. The acoustic inversion results are in general agreement with the grain size analysis of two sediment grab samples, which indicate that more than 80% of the material is composed of well-distributed sand particles of different sizes, the remaining part being shell fragments and silt/clay mixtures.

Original languageEnglish
Title of host publication2015 IEEE/OES Acoustics in Underwater Geosciences Symposium, RIO Acoustics 2015
PublisherIEEE, Institute of Electrical and Electronics Engineers
ISBN (Electronic)9781467370196
DOIs
Publication statusPublished - 18 May 2016
Externally publishedYes
EventIEEE/OES Acoustics in Underwater Geosciences Symposium, RIO Acoustics 2015 - Rio de Janeiro, Brazil
Duration: 29 Jul 201531 Jul 2015

Conference

ConferenceIEEE/OES Acoustics in Underwater Geosciences Symposium, RIO Acoustics 2015
CountryBrazil
CityRio de Janeiro
Period29/07/1531/07/15

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  • Cite this

    Ren, Q. Y., Hermand, J. P., Randall, J., Verbanck, M., & Brehmer, P. (2016). First trial of multi-wavelength vector sensor: Sediment geoacoustic properties obtained from vessel noise off Senegal. In 2015 IEEE/OES Acoustics in Underwater Geosciences Symposium, RIO Acoustics 2015 [7473637] IEEE, Institute of Electrical and Electronics Engineers. https://doi.org/10.1109/RIOAcoustics.2015.7473637