The effects of internal waves on sound speed in shallow waters of the Persian Gulf

The internal waves complicate the propagation process of sound in the water. These waves are considered the main cause of disturbances in sound speed, and now it is known that the internal waves are the dominant parameter in the change process of sea frequency spectrum, as these changes range from many hourly cycles (floating frequency) to almost one daily cycle (inertia frequency). The profile of mass sound speed in shallow waters depends on salinity and temperature gradients in turbulence internal waves. Here, the assumption is that the only probability function source is the turbulence internal waves in a water column. This investigation aims to use the mathematical models to study the internal wave effects on propagation of sound waves in shallow waters and that the waves how affect the sound propagation and depend on what parameters? We used the data gathered from Persian Gulf to calculate the parameters such as: sound speed, floating frequency, the ratio of resulted turbulences in sound propagation by vertical movement, phase functions and internal wave domain. Meantime, based on a given wave length (in the study area: 235 m.), the shape of first mode has been compared to the other modes. The probability density functions have been calculated for two different modes. Comparing the ratio of generated turbulences in sound propagation by vertical movement and horizontal speed of particle, showed the horizontal movement is considerably less than the vertical one and also by increasing the depth (consequently decreasing the floating frequency), vertical movement is raised highly. The highest floating frequency and turbulences generated in sound propagation by vertical movement are found on the places near the water level and this is due to thermocline existence and on the other hand in the same places we have the lowest range of vertical movement.