Effects of Irregular Bathymetry on Hologram Formation of Moving Source in Shallow Water

This paper examines the effect of irregular bathymetry on the holographic reconstruction of the sound field generated by a moving source in shallow water. In this scenario, acoustic waves propagate along the path between the source and receiver. Spatial inhomogeneities in the waveguide, resulting from the complex bottom topography, cause the notable horizontal refraction of acoustic modes. The study focuses on how this horizontal refraction affects the structure of the interferogram and the hologram corresponding to the moving source. This investigation is carried out through numerical simulations that incorporate ray refraction due to irregularities in the waveguide. The interferogram, representing the received sound intensity in the frequency-time domain, and the hologram, obtained via a two-dimensional Fourier transform of the interferogram, are analyzed in the presence of spatial variability caused by non-uniform bathymetry. A key finding is that, despite these irregularities, the hologram retains sufficient structural information to extract and reconstruct source parameters (e.g., range, velocity). The paper also provides a quantitative estimate of the reconstruction error associated with this approach.