Eigenvalue Decline Index of Correlation Matrix for Shallow Water Source Depth Discrimination

Source depth discrimination is important for anti-submarine warfare and marine biology. Given the difference in the vertical correlation of acoustic fields excited by sources at varying depths, a physics-based quantity characterizing the vertical correlation of acoustic field is proposed for passive surface/submerged source classification in a shallow water range-independent waveguide. The eigenvalue decline index of correlation matrix is the ratio of the maximum eigenvalue to the second largest eigenvalue of the receiving signal correlation matrix, which is calculated to characterize the oscillation properties of the correlation coefficient matrix. The eigenvalue decline index is then analyzed and discussed under the simulation condition of the typical isovelocity sound speed profile in shallow water. This decline index presents obvious separability so long as the receiving vertical line array is designed properly. The condition for the vertical correlation characteristics of the acoustic field is that the spacing of the array elements should be no more than one-third of the wavelength. Using the eigenvalue decline index may provide a robust alternative method for binary source depth classification.