Study on non contact acoustic imaging method for non destructive inspection using SLDV and LRAD

We propose a new non-contact acoustic imaging method for nondestructive inspection using scanning laser Doppler vibrometer (SLDV) and long range acoustic device (LRAD). In this method, Surface vibration, which is generated by air borne sound, is measured using SLDV. This time, the styrofoam board (300 × 300 × 100 mm
³
) was buried at 50 mm depth in the concrete are used as a substitute of a cavity in the concrete. As an experimental result, a styrofoam board is clearly imaged by the vibration velocity of the concrete surface. And also, we confirmed the response range of the frequency of a buried object. Clearer image is formed by the optimum frequency response range (OFR) method.