This book is a practical and intermediate level handbook written to describe acoustic emission technique, focusing on the results obtained from different kinds of materials through an engineering point of view. Internal structural modifications of materials such as dislocation motion, plastic deformation, grain boundary sliding or crack propagation are connected to the production of acoustic waves. The possibility of detecting these low amplitude waves, which are known as acoustic emissions, in order to prevent failure represents an interesting and very promising approach that has been applied in several engineering fields. The possibility to monitor the whole history of materials without scanning and accessing from one side only is a great advantage connected with this method, especially if compared or even combined with other traditional techniques. Focus on Acoustic Emission Research offers the reader the information needed to understand the basic principle of the acoustic emission phenomenon and to provide updated information about results obtained for different kinds of materials and large-sized structures. Each chapter, written by invited experts, follows a focused and practical arrangement with subsections describing the measurement principle, the experimental procedures, the results and references. The reader of the book will benefit by the significant hands-on experience that each author transfers into their respective chapter. The volume illustrated provides, in fact, a practical approach to acoustic emission that makes this volume attractive to industrial experts, academic researchers and students.