An acoustic sound speed profiling system is provided. The system includes a sound emitter and a series of sensors or hydrophones spaced vertically in a water column. The sound emitter is a high-frequency sound source adap for mounting on the front end of a passive, towed sonar array. The sound source has a frequency which may be outside the acoustic aperture of the towed array. The series of sensors are located at intervals along and embedded within the array tow cable. The sensors are conventional hydrophones or thin-film hydrophone membranes. During operation of the system, the source transmits high frequency sound, which is received by each sensor along the tow cable of the towed array. Calculation of the speed of sound is determined from the position of the tow cable and the time-of-arrival of acoustic signals at each sensor. There is no interference with the normal operation of the passive towed array.