Observation of Acoustical Signal Fluctuations by Time-Frequency Analysis Methods

In this paper, acoustic data collected in shallow water during INTIMATE00 sea trials are analysed with the aim to detect fluctuations in acoustical signals under the effect of a time-varying environment. Some time-frequency analysis methods, i.e., Gabor Expansion and Wigner-Ville Distribution, have resulted to be adequate to find out fluctuations in the received signals, in particular, such analyses reported different time-frequency behaviour in relation with different tidal conditions. The variations observed in the received acoustic data have been compared with the temperature data collected during the sea trials and the related sound-speed profiles: it has been reported that major fluctuations over time in the acoustic signal occur in correspondence of the sound-speed profile changes linked to environmental variability.