One surface of a component is obliquely ensonified through a liquid or gaseous first medium with a checking sound beam produced by a transmission/reception transducer for defect investigation of the component. A response sound beam, which is reflected back from the surface to the transmission/reception transducer, is received and its delay time in the medium between the transmission/reception transducer and the surface is evaluated. The delay time in the medium determined in this way is taken into account for localization of a defect within the component.