Abstract:

During the SWARM 95 experiments the out-of-plane broadband acoustic propagations were used to examine the effect of azimuth as well as the frequency dependence on the propagation of an acoustic pulse through internal waves. A highly repeatable source (a 40-in. airgun with center frequency of 75 Hz and bandwidth of 50 Hz) was used at different water depths. The environmental data were measured at the source and at the two receiver arrays located approximately 25--30 km away perpendicular to the main propagation track. It is shown that the dominant energy of the propagation is distributed between the first and the second modes. The transfer of energy among the modes as well as the fluctuations of the field are depth dependent as well as time dependent, which can be related to the internal wave characteristics. The coherence of the field in cross range due to the same source signature is also examined.