ИСТИНА

The sound propagation in ultra shallow water was studied by our research group. The experiment was carried out in the rectangular pond approximately 300x20 meters in size. Its depth was about 1 meter. The signal was radiated by the transducer and recorded by a set of point receivers located at different distances from the transducer. It was decided to use a linear frequency modulated signal with 100Hz-10kHz frequency band and 10 seconds duration. Its correlation with the recorded signal is equal to the pond response function. It was shown that only the first mode propagated in the pond. The group velocity frequency dependence was obtained using this method and it was very close to the theoretical one considering a soft bottom. The critical frequency also corresponded the soft bottom model. The attenuation of sound was also studied in a wide frequency range including non-propagating mode. This results are very sensitive to the signal-to-noise ratio. It was shown that the used correlation method significantly improved the quality of obtained characteristics. The performed numerical simulations agreed with experimental results.