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

Abstract: 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.