Calibration for a nondestructive ultrasonic material testing system is provided, the system having a multiplicity of ultrasound transducers which are linearly movable as a whole but are arranged fixed with respect to one another, for example mounted fixed in a single sensor holder. In order to achieve optimal alignment of the sensors with a specimen, the mechanical tolerance-induced offset between the beam direction of the ultrasound transducers and the ideal beam directions is found, for example with the aid of a mean straight line. It is then minimized by using the available degrees of freedom of the sensor holder, for example possible tilting of the sensor holder.