This book presents articles from the World Conference on Acoustic Emission 2019 (WCAE-2019) held at Guangdong, China. The latest research and applications of acoustic emission (AE) are explored, with a particular emphasis on detecting and processing AE signals, the development of AE instrument and testing standards, AE of materials, engineering structures and systems, including the processing of collected data and analytical techniques. Numerous case studies are also included. It brings together leading academicians and professionals in the field to foster collaboration and to enhance research in this important area, with wide ranging applications.