UACE2017 Proceedings: Acoustic coherence in fluctuating oceans: Analysis of the ALMA-2016 campaign

• Session:
  Design of new experimental facilities to address future problems in underwater acoustics
• Paper:
  Acoustic coherence in fluctuating oceans: Analysis of the ALMA-2016 campaign
• Author(s):
  Gaultier Real, Dominique Fattaccioli
• Abstract:
  The authors present the analysis of the acoustic propagation measurements conducted in November (7th-17th) 2016 near the shores of North East Corsica using the ALMA (Acoustic Laboratory for Marine Applications) system. The campaign is fully described in a companion paper (see Fattaccioli & Real, session “Design of new experimental facilities to address future problems in underwater acoustics”). The array consisted of 128 hydrophones arranged in a comblike configuration (4x32 vertical linear arrays). A moored pinger, 9 km from the arrays, transmitted signals with a 1 minute repetition rate. The study of the influence of fluctuations in the water column (typically internal waves, very frequent in shallow waters and coastal environments) on sound waves propagation is aimed.\nTo do so, fluctuations of the received wavefronts at various frequencies (from 1kHz to 13kHz) on each of the four joint vertical linear arrays are shown. Statistics of the recorded data are also provided, including Mutual Coherence Function (MCF), radius of coherence and array gain degradation. The non-stationarity and non-uniformity of the received data highlights the influence of spatio-temporal variations of the medium.\nIn complement, CTD casts were performed at various times at the source and receiver locations. A CTD chain was deployed next to the receiving array so that environmental fluctuations are monitored during the campaign whole duration. The presence of a strong thermocline is shown by the data analysis of these tools.\nSome comparison with propagation models, both in terms of quantitative (coherence) or qualitative (regime of fluctuation) analyses, will be available as well.
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Contact details

• Contact person:
  Dr Gaultier Real
• e-mail:
  
• Affiliation:
  DGA Techniques Navales
• Country:
  France