Passive acoustic Measurements of flow velocity in the ocean

Oleg A. Godin, Michael G Brown, Neil J. Williams, Nikolay A. Zabotin, Liudmila Y. Zabotina

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Measurements of velocity of oceanic currents are crucial for evaluating heat and mass transport, monitoring ocean dynamics, and understanding the ocean's role in climate. Reciprocal transmissions of acoustic signals provide a way to measure path-averaged current velocity in the ocean with high temporal resolution, on a large scale, and over extended periods of time. This approach is based on measurements of acoustic nonreciprocity, which is defined as differences between travel times or other acoustic quantities corresponding to sound propagation in opposite directions between two points. Acoustic nonreciprocity, which vanishes in motionless media, is a direct, sensitive measure of fluid motion, and is insensitive to uncertainties in the sound speed field and geometry of the experiment. The use of active reciprocal transmissions for ocean remote sensing applications is limited by capital and operational costs associated with low-frequency acoustic sources as well as concerns about potential impacts of transmissions on marine life. Underwater acoustic noise interferometry offers an alternative to active remote sensing by replacing probing signals generated by a dedicated source with two-point cross-correlations of diffuse ambient noise. Theory predicts that the cross-correlation function of diffuse noise measured at two locations in a generic inhomogeneous moving medium results in approximations to Green's functions describing sound propagation in opposite directions between the two measurement points; positive and negative lags correspond to propagation in opposite directions. Thus, two-point correlation functions allow one to quantify flow-induced acoustic nonreciprocity. In this paper, we use the data obtained in a noise interferometry experiment in the Straits of Florida to investigate the feasibility of passive remote sensing of currents in the ocean. We present the first experimental demonstration that acoustic nonreciprocity induced by oceanic currents can be measured by noise interferometry and that the current velocity can be retrieved from the acoustic noise cross-correlations.

Original languageEnglish (US)
Title of host publication22nd International Congress on Sound and Vibration, ICSV 2015
PublisherInternational Institute of Acoustics and Vibrations
ISBN (Electronic)9788888942483
StatePublished - 2015
Event22nd International Congress on Sound and Vibration, ICSV 2015 - Florence, Italy
Duration: Jul 12 2015Jul 16 2015

Other

Other22nd International Congress on Sound and Vibration, ICSV 2015
CountryItaly
CityFlorence
Period7/12/157/16/15

Fingerprint

acoustic measurement
oceans
flow velocity
acoustics
cross correlation
remote sensing
interferometry
sound propagation
ocean dynamics
straits
underwater acoustics
temporal resolution
travel
climate
Green's functions
time lag
low frequencies
costs
heat
propagation

ASJC Scopus subject areas

  • Acoustics and Ultrasonics

Cite this

Godin, O. A., Brown, M. G., Williams, N. J., Zabotin, N. A., & Zabotina, L. Y. (2015). Passive acoustic Measurements of flow velocity in the ocean. In 22nd International Congress on Sound and Vibration, ICSV 2015 International Institute of Acoustics and Vibrations.

Passive acoustic Measurements of flow velocity in the ocean. / Godin, Oleg A.; Brown, Michael G; Williams, Neil J.; Zabotin, Nikolay A.; Zabotina, Liudmila Y.

22nd International Congress on Sound and Vibration, ICSV 2015. International Institute of Acoustics and Vibrations, 2015.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Godin, OA, Brown, MG, Williams, NJ, Zabotin, NA & Zabotina, LY 2015, Passive acoustic Measurements of flow velocity in the ocean. in 22nd International Congress on Sound and Vibration, ICSV 2015. International Institute of Acoustics and Vibrations, 22nd International Congress on Sound and Vibration, ICSV 2015, Florence, Italy, 7/12/15.
Godin OA, Brown MG, Williams NJ, Zabotin NA, Zabotina LY. Passive acoustic Measurements of flow velocity in the ocean. In 22nd International Congress on Sound and Vibration, ICSV 2015. International Institute of Acoustics and Vibrations. 2015
Godin, Oleg A. ; Brown, Michael G ; Williams, Neil J. ; Zabotin, Nikolay A. ; Zabotina, Liudmila Y. / Passive acoustic Measurements of flow velocity in the ocean. 22nd International Congress on Sound and Vibration, ICSV 2015. International Institute of Acoustics and Vibrations, 2015.
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