Abstract:

Various aspects of the monitoring of ship traffic using correlation of signals recorded by a pair of hydrophones are considered and demonstrated on real signals recorded in the Hudson River. The underwater acoustic noise generated by ships reaches the various hydrophones with a delay depending on their relative positions. That delay can be extracted by cross‐correlation and can serve as a basis for determination of the direction of the ship. This method allowed finding directions for several ships in heavy traffic of Hudson River. The vessel triangulation can be done using information from two or more appropriately located hydrophone pairs. Another application demonstrated is separation of the acoustic signature (noise spectra) from several ships. The last application is the estimation of the ship noise modulation spectrum that is related to propeller and shaft rotation by means of short time cross‐correlation. Comparison with the conventional detection of envelope modulation on noise method shows a close match. [This work was partially supported by ONR Project N00014‐05‐1‐0632: Navy Force Protection Technology Assessment Project and by the U.S. Department of Homeland Security under Grant No. 2008‐ST‐061‐ML0002.]