During the Shallow Water 2006 (SW06) experiment, several internal wave (IW) events were recorded by moving and stationary instruments simultaneously with the acoustic propagation tests. More than 50 IW events were recorded using the University of Delaware's R/V Sharp's radar. On this ship, a J15 sound source transmitted various acoustic signals at different bearings and ranges to the Woods Hole Oceanographic Institution's vertical and horizontal hydrophone arrays. During one of the IW events, the acoustic source was kept at a constant water depth while moving in horizontal plane with the advancing internal wave front. This internal wave packet, named Event 50, was also recorded by R/V Oceanus radar a few kilometers away. The reason for placing the sound source on the advancing IW front was to examine the effects of azimuthal variability of the waveguide on the acoustic propagation. A detailed transition of the waveguide as the internal wave progressively occupied the acoustic propagation track between the source and receiver is reported. It is shown that the intensity peaks at small angles between the acoustic track and the internal wave front where sound intensity focusing and defocusing occurs.

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