At the M.I.T. Commencement, General George C. Kenney warned his listeners that sound would be used as a weapon in future warfare. Scientists bent on more peaceful research tell us that sound leaves, some of them beyond our hearing, will kill bacteria, homogenize milk, speed chemical reactions, deled flaws in metals, mix paint, precipitate dust particles from smoke, and increase the yield from plant seeds. And at Columbia University ultrasonic waves have penetrated the skulls of animals to perform a knifeless surgery. Shall sound kill or cure?