Ultrasonic transducers are key devices for important applications such as medical treatments, non-destructive testing and precision alignment. This book will review the materials, design and applications of ultrasonic transducers, focussing on recent developments and issues. Part one will provide an introduction to the theory of elastic vibrations in solids and the modelling of ultrasonic transducers. Part two will cover characterisation of ultrasonic transducer performance. Part three will focus on the materials such as piezoelectric ceramics and the design of ultrasonic transducers. Part four contains chapters on applications of ultrasonic transducers in devices and systems including SAW devices, ultrasonic motors and therapeutic ultrasound.