A Method for Determining Normal Mode Number in Shallow Water Waveguide Based on Dispersion Curves

In order to determine the normal mode numbers from the received signal of broadband pulse sound source in shallow water waveguide, a method for determining normal mode numbers in shallow water waveguide based on Bayesian estimation theory is proposed in this paper. The dispersion curves extracted from the measured data is used as the input signal of Bayesian inversion theory, and the replica is calculated by dispersion formula, which is composed of bottom reflection phase shift parameter, depth, propagation range and average sound velocity in water. The bottom reflection phase shift parameter is used to describe the bottom geoacoustic parameters, which can reduce the number of inversion parameters and prevent interference between parameters. Then a double cost function for normal mode number and marine environmental inversion parameters is established, the determination of normal mode number takes precedence over parameters inversion. Finally, the normal mode number is determined accurately by comparing the dispersion curves calculated from the inversion results with the measured results. The method is not only simple and easy to operate, but also Significantly improve the calculation speed and inversion efficiency. The experimental data processing results prove the effectiveness and accuracy of the method.