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Temporal variability of Signal Detection Range (SDR) with respect to measured noise level and sound speed is examined. An N x 2D acoustic model which included bathymetric variations, was used to study detection ranges for an area in Arabian Sea. Azimuthal and seasonal SDR at octave bands within 500 Hz were determined at different receiver depths. Study shows that seasonal change in sound speed profile resulted in high SDR and noise level in winter at the location. Study also confirms the significant seasonal difference in detection range corresponds to the cut off frequency at 160 Hz. Detection range for a receiver at a depth 40 m is observed to be high across the azimuth and seasons of study. [ABSTRACT FROM AUTHOR]

During November 2017, an active source seismic survey was performed in Andaman Sea to study the acoustic propagation characteristics. High power low frequency acoustic signals generated by 20-air gun array onboard Research Vessel Samudra Ratnakar were recorded from INS Sagardhwani at four different depths within 8 km ranges in shallow and deep waters. The received level was estimated using root mean square and power spectral values. Amplitude levels were analysed with respect to arrival time variation with frequency and is presented. [ABSTRACT FROM AUTHOR]