Acoustical Inversion Method using Cepstrum Analysis of Underwater Ship Noise

Abstract

This paper presents an acoustical inversion method using cepstrum analysis of a transiting ship noise in shallow waters. Through cepstrum analysis, we can extract the multipath arrival structure from the ship radiated noise recorded by a hydrophone. The multipath structure comes from the interferences between a direct arrival and multiple reflections from the sea surface and the bottom, which depends mainly on the source-receiver configuration and the sound speed profile in water column. A ship underwater noise measurement tests were performed at South Sea of Korea. By using DGPSs, we recorded the locations of the target ship and the buoy from which hydrophones were suspended. The measured sound pressure levelcan be converted into the source level using the slant range from the acoustic center of the ship to each hydrophone based on the geometrical spreading. However, it is hard to expect that the locations of the ship and the buoy coincide with the acoustic center and the hydrophone position. In order to estimate the acoustic center and the hydrophone position, thus, we applied the inversion method to the measured signal cepstrums. Finally, the inversion results were examined tovalidate the suggested method.