**1. Introduction**

Acoustic emission (AE) techniques have successfully been used for assuring the structural integrity of large rocket motorcases since 1963 [1], and their uses have been expanded to ever larger structures [2,3], especially since the structural health monitoring (SHM) of large structures has become an urgent task for engineering communities globally. The needs for advanced methods of AE monitoring are felt most keenly by those dealing with aging infrastructure. Many publications have appeared covering various aspects of AE techniques, but documentation of actual applications of AE techniques has been limited mostly to reports of successful results without technical details that allow objective evaluation of the results, except for some exceptions in the literature where special applications were detailed [4–6]. In this Special Issue of the Acoustics section of Applied Sciences, we sought contributions, like the exceptions cited here, which describe case histories of AE being applied to large structures. That is, papers that have achieved the goals of SHM and do so by giving adequate technical information supporting the success stories. Gathered here are 14 such articles that cover structures from aerospace and geological structures, bridges, buildings, factories, nuclear facilities, etc.
