A class of hydrodynamic oscillators is being developed which shows considerable promise for sonic and ultrasonic applications involving large acoustic power requirements. These devices convert liquid flow energy into acoustic energy with conversion efficiencies that can exceed 50% in favorable circumstances. The performance characteristics of a low‐frequency (1000 cps) and a high‐frequency (20 kcps) oscillator will be described. Problems associated with the delivery of the generated acoustic energy to the site of its application will be discussed. [This work was supported by the Office of Naval Research.]