Method and system for remote sound speed measurement

A method of estimating a sound speed profile, the method comprising:

• transmitting a first acoustic signal from a first location towards a plurality of reflectors comprising at least a first scattering layer at a first depth and a second scattering at a second depth;
• transmitting a second acoustic signal from a second location towards the plurality of reflectors;
• receiving a first scattered signal at a third location from the plurality of reflectors, the first scattered signal comprising a plurality of echoes of the acoustic signal reflected by the first and second scattering layers;
• receiving a second scattered signal at a fourth location from the plurality of reflectors, the second scattered signal comprising a plurality of echoes of the acoustic signal reflected by the first and second scattering layers;
• estimating at least a first and second travel time based on at least one of the first or second scattered signals;
• generating a cross-correlation signal comprising a cross-correlation of the first scattered signal and the second scattered signal;
• estimating at least first and second travel time differences based on the cross-correlation signal;
• estimating the first and second depths;
• estimating a sound speed to the first and second depths;
• and
• estimating a sound speed profile based on the estimated depths and estimated sound speeds.

A system for estimating a sound speed, the system comprising:

• means for transmitting an acoustic signal from a first location;
• means for receiving a first scattered signal at a second location, the first scattered signal comprising a plurality of echoes of the acoustic signal reflected by a scattering layer;
• means for receiving a second scattered signal at a third location, the second scattered signal comprising a plurality of echoes of the acoustic signal reflected by the scattering layer;
• means for receiving a third scattered signal at a fourth location, the third scattered signal comprising a plurality of echoes of the acoustic signal reflected by the scattering layer;
• means for estimating a travel time based on at least one of the first, second, or third scattered signals;
• means for generating a cross-correlation signal comprising a product of at least two of the first, second, and third scattered signals;
• means for estimating a travel time difference based on at least the cross-correlation signal;
• and
• means for estimating a sound speed based on the estimated travel time and the estimated travel time difference.

A non-transitory computer-readable storage medium having instructions stored thereon which, when executed by a processor, causes a method of estimating a sound speed to be performed, the method comprising:

• estimating a travel time based on at least one of a first scattered signal, a second scattered signal, or a third scattered signal, wherein each of the first, second, and third scattered signals comprises a plurality of echoes of an acoustic signal reflected by a scattering layer;
• generating a cross-correlation signal comprising a product of a least two of the first, second, and third scattered signals in accordance with the bistatic invariance principle;
• estimating a travel time difference based on at least the cross-correlation signal;
• and
• estimating a sound speed based on the estimated travel time and the estimated travel time difference.