An inversion method of sound speed profile based on waveguide invariant

The ocean hydrological environment is non-uniform in time and space, and the measured sound field results are often disturbed by various environmental factors, which causes a certain error between the inverted sound speed and the actual seawater sound speed. To reduce the influence of complex environments and improve the environmental adaptability of sound speed profile inversion, this paper proposes a new method for sound speed profile inversion using the distribution of waveguide invariant spectrum values. Based on the frequency-distance interference image of the sound field, the sensitivity of the waveguide invariant spectrum to changes in the sound speed profile is analyzed, and a corresponding cost function is constructed to invert the sound speed profile. Through two-dimensional Fourier filtering and sampling, the influence of horizontal sound speed disturbances and seabed fluctuations on inversion results is further reduced. Combined with the ray-normal mode method, broadband optimization is carried out efficiently to improve inversion efficiency. Simulation and measured results show that the inverted sound speed profile using this method agrees well with the real value, with root mean square error within normal ranges, and it demonstrates good adaptability to environmental factors such as horizontal sound speed changes and seabed fluctuations.