Ultrasonics has been recognised not only as a viable and dependable tool to prognosticate diseases in medical practices but also a prevailing technique in non-destructive detection and manufacturing. In this book, the authors study the theory, techniques and practical applications of ultrasonics. Topics include mechanochemical cleavage of DNA by ultrasound; using ultrasonic wave transmission and wave reflection methods to monitor the setting and hardening process of cement based materials; ultrasonic spray-pyrolysis process for materials processing; ultrasonic assisted fixed abrasive machining of hard-brittle materials; dynamics and kinetics of super-cooled liquids under ultrasonic field; mathematical model of a travelling wave ultrasonic motor; ultrasonic array image in anisotropic weld structures; and ultrasonics in machining operations.