Acoustic Emission Testing (AET) is a non-destructive evaluation technique used to monitor material behavior under load. Unlike other non-destructive testing (NDT) methods, AET can track changes in material behavior over time without moving components, making it unique. It detects crack propagation, both on the surface and inside materials, and is an important addition to NDT methods. AET is used to survey structures for geometric defects and to complement visual inspections. AET has been successfully applied to various materials, but its application depends on the material's heterogeneity and structure. The technique ranges from scientific/experimental to industrial/routine applications. While the setup for AET appears simple, obtaining reliable results requires solving many issues. The book addresses AET's principles, applications, and challenges. Part A covers the basics of AET, including its history, fundamentals, sensors, parametric analysis, signal-based analysis, source localization, and source mechanisms. Part B focuses on practical applications, such as AET in concrete, rock, wood, superstructures, substructures, wireless techniques, and opportunities, limitations, accuracy, and skill requirements. AET is considered a "passive" technique because it detects defects as they develop during testing. It is useful for early detection of failures in structures. AET is often used to detect early-stage damage, long before a structure completely fails. The technique is compared to seismology, as both involve detecting energy release during failure processes. AET is sensitive to irreversible deformations in materials and can detect new crack formation and existing crack progression. It is useful for monitoring real load conditions in structures. However, AET has limitations, such as the need for sensitive sensors and reliable amplifiers due to the low signal-to-noise ratio. Data processing techniques are essential for detecting and interpreting AET signals. The book discusses the development of AET, its history, and key contributors. It covers the fundamentals of AET measurement, sensor technology, and system response. The book also addresses the challenges and future developments in AET, including the use of wireless sensor networks and advancements in microelectronics and sensing techniques. The book is a comprehensive resource for understanding AET and its applications in various fields.Acoustic Emission Testing (AET) is a non-destructive evaluation technique used to monitor material behavior under load. Unlike other non-destructive testing (NDT) methods, AET can track changes in material behavior over time without moving components, making it unique. It detects crack propagation, both on the surface and inside materials, and is an important addition to NDT methods. AET is used to survey structures for geometric defects and to complement visual inspections. AET has been successfully applied to various materials, but its application depends on the material's heterogeneity and structure. The technique ranges from scientific/experimental to industrial/routine applications. While the setup for AET appears simple, obtaining reliable results requires solving many issues. The book addresses AET's principles, applications, and challenges. Part A covers the basics of AET, including its history, fundamentals, sensors, parametric analysis, signal-based analysis, source localization, and source mechanisms. Part B focuses on practical applications, such as AET in concrete, rock, wood, superstructures, substructures, wireless techniques, and opportunities, limitations, accuracy, and skill requirements. AET is considered a "passive" technique because it detects defects as they develop during testing. It is useful for early detection of failures in structures. AET is often used to detect early-stage damage, long before a structure completely fails. The technique is compared to seismology, as both involve detecting energy release during failure processes. AET is sensitive to irreversible deformations in materials and can detect new crack formation and existing crack progression. It is useful for monitoring real load conditions in structures. However, AET has limitations, such as the need for sensitive sensors and reliable amplifiers due to the low signal-to-noise ratio. Data processing techniques are essential for detecting and interpreting AET signals. The book discusses the development of AET, its history, and key contributors. It covers the fundamentals of AET measurement, sensor technology, and system response. The book also addresses the challenges and future developments in AET, including the use of wireless sensor networks and advancements in microelectronics and sensing techniques. The book is a comprehensive resource for understanding AET and its applications in various fields.