Simultaneous Nearby Measurements of Acoustic Propagation and High-Resolution Sound-Speed Structure Containing Internal Waves

During the 2006 Shallow Water (SW06) experiment, simultaneous measurements were made of the sound-speed field as a function of range and depth associated with nonlinear internal waves and acoustic propagation at frequencies of 2-10 kHz over a 1-km path. The internal waves were measured by a towed conductivity-temperature-depth (CTD) chain to get high resolution. These measurements were coordinated so that the nonlinear waves could be interpolated onto the acoustic path, allowing predictions of their effects on the acoustics. Using the measured sound-speed field, the acoustic arrivals under the influence of the internal waves are modeled and compared to data. The largest impact of measured moderate amplitude internal waves on acoustics is that they alter the arrival time of the rays which turn at the thermocline.