Disclosed is a sonotrode (10) for generating an ultrasonic field in industrial production processes for reducing and eliminating foaming of liquid products (3). The sonotrode (10) includes a main body part (1) with connecting means for connection with a high frequency generator and has a front face from which the ultrasonic field is directed to the desired spot or area of the product (3) to be de-foamed. The main body part (1) has the shape of a rectangular or square block element having a reduced diameter part on the side of the front face which is enlarged compared to the latter. The front face is concave in shape in relation to a product (3) surface for focusing the ultrasonic field to a specific area of the product (3) foam to be treated in a concentrated form compared to a non-focused ultrasound. The front face has a rectangular form with a round concavity in the direction of the longitudinal axis in the shape of a rounded groove or channel.
