Propagation of ultrasonic radiation in the presence of seabed topography in the North Indian Ocean

Due to the good propagation of sound waves in the ocean, sound energy is used to reveal the subsurface of the sea. In order to take advantage of the different characteristics of the environment in which sound is emitted, modeling and simulation of sound waves should be used. For this purpose, the environmental factors should be investigated and the way of sound rays propagation and the efficiency of sonar should be simulated in different conditions and in different times and places. This research is designed with the aim of investigating the effects of topographical shape on the propagation of ultrasound rays. In this research, firstly, the environmental data of the study area, which includes salinity, temperature and depth data in the northern Indian Ocean, has been extracted from international databases (such as HYCOM, GEBCO, WOA, etc.). Then, using the beam method, the propagation of ultrasonic waves in the presence of roughness of the seabed has been simulated. First, changes in hydrophysical parameters were analyzed using temperature and salinity data in the Indian Ocean and with the help of graphic models. Then, using Mackenzie's formula, the speed of sound in these sections was calculated and analyzed. With the help of the existing acoustic model, pressure changes were first checked and then this output was used to calculate the amount of return signal from a hypothetical underwater target. The results of different simulation scenarios of ultrasonic beam propagation show that when the source is placed under the thermocline layer, the acoustic beams are deflected downwards. As the frequency increases, the transmission loss increases and the intensity of the acoustic pressure decreases. Because the amount of absorption of sound waves increases with increasing frequency.