Estimation of bubble size and distribution and the effects of bubbles on high-frequency transmission

Measurements of bubble size and distribution in the ocean bubble layer, wind speed, and variation of ocean environment were made continually over a four-day period in an experiment conducted in the South Sea of Korea during 17-20 September 2007. Theoretical background of bubble population model and bubble effects on sound speed indicate that bubble population is a function of the depth, range and wind speed. The sound speed appears to depend on the sound frequency. Observational evidence exhibited that the middle size bubblespsila population fit the model very well, however, small ones can not follow the model which probably due to they have a short lifetime. Meanwhile, there is also a hysteresis effect of void fraction comparing with the void fraction model. Observational evidence also indicates that strong changes in the sound speed are produced by the presence of swarms of micro bubbles especially from 7 kHz to 50 kHz, and also the calculation results are consistent with the measured data in the high frequency band, but inconsistent in the low band.