A method and device for non-destructive testing of a plate material

It is disclosed a method and device for testing a plate material (1) for the presence of pits and holes (3), said method including the steps of; transmitting an acoustical signal from a transmitting transducer (2) facing the plate material (1) and positioned in a distance from the plate material, the frequency of the transmitted signal and the angle of incidence of the signal towards the plate material being adapted to promote the formation of Lamb signals in the plate material, receiving an acoustical signal returned from the plate material in a receiving transducer (4) also facing the plate material: at a distance from the material, the receiving transducer (4) being located in a distance from said transmitting transducer (2) along the direction of the plate material, time gating the received signal identifying a tail part (8) carrying information from Lamb signals travelling In the material, and determining the energy content in said Lamb mode part of the signal.