Conventional ultrasonic methods based on ultrasonic characteristics in thelinear elastic region are mainly sensitive tomature defects butare much less responsive tomicro-damage or incipient material degradation. Recently, nonlinear ultrasonic characteristics beyond the linear ultrasonic amplitude range have been studied as a method forovercoming this limitation, and hence, many researchers are engaged in theoretical, experimental, and various application studies. However, the nonlinear ultrasonic characteristics are quite exacting compared tothelinear phenomena so that they require vast experience and high proficiency in order toobtain proper experimental data. Actually, many researchers, especially beginners including graduate students, have difficulty in reliably measuring nonlinear ultrasonic characteristics. This book provides key technological know-how fromexperts withyears ofexperience in this field, which will help researchers and engineers to obtain a clear understanding and high quality data in thenonlinear ultrasonic experiments and applications.