The invention relates to a device for generating an ultrasonic field having frequencies between 0.9 MHz and 4 MHz in an object, preferably in water or in human tissue, the device comprising a piezo element (1) affixed to a coupling plate (5), the coupling plate emitting the ultrasonic field (6) into the object, wherein the dimensions of the coupling plate are chosen such that the intensity of the ultrasonic field (6) emitted into the object is minimized in a depth deeper than 70 mm.
