Professor Hunt once asked, "Can you 'blow' a whistle under water?" This question was perhaps the first of a series of events that has led to the emergence of a new power-conversion technology for the efficient conversion of hydraulic power to acoustic or vibratory power. This hydroacoustic power-conversion process embodies flow-switching techniques that are analogous to switching methods that are employed in electronic dc to ac power-conversion practice.

      The hydroacoustic technology has been developed for the generation of high-power underwater sound for communication and echo location and for such industrial uses as high-frequency rotary percussion rock drilling and pile driving. The origins of the power-conversion technology are reviewed, analytical models used for predicting equipment performance are described, and illustrations of specific applications anticpated by Hunt and the author are set forth.