This article presents basic research results for production of oil in water emulsions under ultrasonic irradiation, A new theoretical model supports experimental work, Special attention is given to the transfer of batch experiments to continuous emulsification processes, Our experimental findings prove that final drop size essentially depends on specific power density, Drop size decreases with increasing residence time in the ultrasonic field until a system specific, minimum drop size is obtained, Ultrasonic irradiation leads to turbulent flow conditions on a macroscopic and a microscopic scale, Our model based on the theory of turbulent drop break up predicts drop size and can be used to design equipment for ultrasonic emulsification.