Beam intensity resampling-based source depth estimation by using a vertical line array in deep water

Abstract

The interference characteristics between the direct and surface-reflected paths in deep-water reliable acoustic path (RAP) environment contain the information of source depth. For the narrowband case, the source depth can be estimated by applying a modified Fourier transform to the beam intensity series in the sine domain of the receiving angle, which was first published by McCargar and Zurk [(2013), J. Acoust. Soc. Am. 133(4), EL320-EL325]. However, in practical RAP environment, the imperfect periodicity of the beam intensity series as well as the inappropriate reference sound speed often degrades the accuracy of this method. To address this problem, this paper designs a pre-processing resampling scheme to modulate the beam intensity series. Given a minor amount of priori environmental information, the proposed resampling function including a specified reference sound speed can effectively enhance the periodicity of the beam intensity series, thereby enables the modified Fourier transform to achieve higher accuracy. The effectiveness and superiority of the proposed method are experimentally demonstrated with the data collected in the South Sea of China. The results show that the proposed resampling scheme can reduce the depth estimation bias by about 12%.