Noncontact acoustic inspection technology using acoustic irradiation induced vibration and high-sensitivity laser Doppler vibrometer

Abstract Noncontact acoustic inspection using acoustic irradiation induced vibration and a high-sensitivity laser Doppler vibrometer is a technique capable of detecting defects near the surface of concrete structures at long distances without contact. Since it fundamentally utilizes flexural resonance, it can be used as an alternative to hammering inspection. Verification experiments have already been conducted on tunnel ceilings with curved surfaces, bridge decks over 30 meters apart, uneven shotcrete in underground cavities, and tile exterior walls using airborne acoustic excitation, demonstrating that inspection results similar to those obtained with hammering inspections are possible. This paper describes the overview of this method and provides examples of its application to actual structures.