Abstract This paper describes a new crack tip diffraction approach using a set of angle beam and direct contact transducers. In this approach, a crack height is calculated from a time di fference from two echoes of a tip-diffracted longitudinal wave, which arise after an incident wave from the angle beam transducer impinges the crack. The two echoes are detected by the d irect contact transducer which lies on the opposite surface of and over the crack. One echo is related to the wave traveling directly from the tip, and the other is the wave after back w all reflection. The new approach has been demonstrated by applying to height measurements of crack-like slits which are machined in welded specimens made from austenitic stainless steel.