Passive acoustic classification of vessels in the Hudson River.

Stevens Institute of Technology is conducting research aimed at the development of a low‐cost passive acoustic system for detection and classification of underwater and surface threats. The experimental system is comprised of a hydrophonearray and a stand alone acoustic buoy. Video and photographs of the passing ships were also captured simultaneously during the acoustic measurements. For classification purposes special attention was paid to extraction of the specific parameters of vessel acoustic signaturesin high‐frequency band (10–60 kHz) using detection of envelope modulation on noise algorithm. The spectrum of the noise envelope contains shaft and blade frequencies and their harmonics. Parameters extracted include the frequency of the fundamental peak of the ship noise emission, the amplitude modulation of the fundamental tone, the number of peaks found in the spectrum, the slope of the spectral peaks, as well as the calculation of the total harmonic distortion. Parameters extracted from various re...