Geoacoustic inversion of towed line array in range-dependent environment

Matched-field inversion (MFI) is an effective method which can infer the seabed parameters quickly. Much previous works on MFI uses a vertical line array (VLA). But, it can not be carried out in large area due to the poor mobility. Moreover, in the range-dependent environments, especially, with the increase of range between source and receiver, variation in the environment can reduce the prediction capability of the matched-field processor due to inaccuracies in the modeling. The horizontal line array (HLA) offers an advantage in terms of system mobility. The source can be towed together with the HLA, and kept at short range separations. MFI degradation due to environmental variability will be minimized or eliminated. This paper investigates the geoacoustic inversion with a towed HLA. Low frequency broad-band source signal and linear matched-field processor for geoacoustic inversion are applied, and the Bayesian and Monte Carlo methods are introduced to analyze the posterior probability density (PPD). The PPD results indicate that the geoacoustic inversions are performed well using the towed line array, and the inversion results tend to be more convergent and credible as the number of frequencies and length of HLA increase. The transmission loss is also calculated. Compared with the true transmission loss, the result indicates that the acoustic field performance prediction by using inverted parameters has small error.