Characteristics of surface reflective path in acoustic channel with sinusoidal moving surface

Sea-surface movement induces the Doppler shift in acoustic signals propagating in the ocean and it also affects coherent propagation. For an observation of moving surface effect on acoustic channel, an experiment is conducted in the towing tank at Seoul National University. The delay time of single surface bounce path from the measurement data shows periodic time dependency, which is caused by the periodic sinusoidal surface. The ray-based propagation model is used to analyze the effect of moving surface. It is applied to the experimental environment and its results are compared with the measurement data. The difference between delay times of single surface bounce path from the model and measurement data are within the error caused by arrangement of source and receiver. Using the model, the delay times of single surface bounce path are observed according to source depth and surface wave height to investigate the effect of moving sinusoidal surface. As source depth or surface wave heights increases, the maximum path length difference of single surface bounce path increases. Thus, the frequency shift due to surface movement increases with increasing source depth and surface wave height.