The ultrasonic guided wave is an efficient tool for structural health monitoring (SHM) due to its large inspection distance and high sensitivity to structural properties. However, the active guided wave method requires a wave generator and a power amplifier, which, in many scenarios of online monitoring, reduce the structural integrity and reliability and are also a heavy burden for power consumption. Flow-induced and mechanical random vibrations occur naturally during the flight of an aircraft and automatically produce passive guided waves with no need for wave excitation equipment, which thus have great potential for online SHM. In this talk, we will show how ambient random guided waves can be used for passive SHM. Recent progress by our research group on this topic will be introduced, including the numerical study of ambient noise distribution in wing structures, manipulation of passive guided wave propagation, signal processing for recovery of diffuse field, passive extraction of dispersion curve, and applications to ice detection and bolt looseness detection. The proposed passive detection methods are verified via both laboratory and wind tunnel experiments.

Dr. Xun Wang received his Ph.D. in "Estimation of multiple sound sources with data and model uncertainties" in Dec 2014 from University of Technology of Compiègne, France. He was a postdoctoral fellow at Aix-Marseille University, France, and a Research Associate at Hong Kong University of Science and Technology from 2016 to 2020. He joined Beihang University, China, in Apr 2020 and has been a Full Professor since Feb 2022. Dr. Xun Wang has published over 50 research papers in leading journals in acoustics and signal processing such as MSSP, JSV, and JASA. He has been awarded more than 10 research grants as PI, including three grants from the National Natural Science Foundation of China. His research interests include acoustical inverse problems, structural health monitoring, and acoustic imaging.