Improving resolution and SNR of correlation function with the increase in bandwidth of recorded noise fields during estimation of bottom profile of ocean

Abstract

Cross-correlation of coherent wave fronts of acoustic ambient noise fields gives an estimation of the bottom profile of ocean. Hydrophones are used to record the noise fields. Averaging time needed for estimating depth of sea bed depends on the number of coherent wave fronts extracted from the noise fields. In the current approach of depth estimation if only two hydrophones are used to record the acoustic noise fields, then it takes large amount of averaging time to extract sufficient amount of coherent wave fronts for estimating depth of sea bed. Use of a vertical array of hydrophones for noise field recording and later by combining the cross- correlation of all hydrophone pairs of the vertical array a stronger signature can be obtained and this greatly reduces averaging time. Reduction of averaging time can be expressed as increase in signal to noise ratio (SNR) and resolution of correlation function. Main goal of this paper is to increase SNR and resolution of correlation function using only two hydrophones and proper use of bandwidth of recorded noise fields. It is shown that recording large bandwidth signals in two hydrophones greatly increases SNR and resolution of correlation hence reduces the averaging time needed for estimating depth of sea bed. Results of this paper were verified using mathematical expression and simulation. Show more