The sensitivity of noise directionality to geo-acoustic parameters of bottom in shallow sea

摘要

The vertical directionality of ambient noise in shallow water is a relatively stable feature of noise, so it is possible to use it to do geo-acoustic inversion. In order to determine the inversion strategy and improve the inversion accuracy, the sensitivity of the vertical directionality to the acoustic parameters of the bottom need to be analyzed before the inversion is performed. Considering the directivity of noise source, the attenuation in the water and the influence of the boundary reflection loss, the vertical directionality based on wind-generated noise is obtained. Firstly, vertical directionality is calculated based on single layer bottom, it is shown that the directionality is sensitive to sound speed at all angle, is sensitive to density at steeper angle, and is sensitive to attenuation below the critical angle. Secondly, double layer bottom (including sediment) is modeled, compared with the parameters in the seabed, the vertical directionality is less sensitive to the parameters in sediment. With the increase of the sound speed in sediment, the peak value of directionality decreases. And the directionality is closely related to the frequency when considering the sedimentary layer.