Ultrasonic Transducers

Preface

Kentaro Nakamura

Ultrasonic waves are useful for detecting and evaluating objects in any kind of medium: gas, liquid or solid, except for a vacuum. Ultrasonic waves have been a practical and powerful tool for several decades, particularly for medical diagnostics in hospitals and nondestructive testing in industry, because electromagnetic waves attenuate rapidly in the human body and metal objects. The safety of ultrasonic waves is, in general, high in comparison with X-rays, and practical measurements and imaging can be carried out with less expensive devices than other methods. The low propagation speed of ultrasonic waves is also a useful feature for measurement and imaging, since the time of flight can be easily used to estimate ...