Physical Acoustics: Principles and Methods, Volume XIII is a six-chapter text that covers a variety of topics in physical acoustics, including the principles of ultrasonic waves, plate modes, diffraction, mode vibrators, ray theory, and acoustic emission. Chapter 1 deals with the theory and application of anelasticity in studying various types of relaxations, such as point defect, grain-boundary, thermoelastic, phonon and electron relaxations, and magnetic relaxations. Chapter 2 presents the different methods used in studying the very important Type II superconductor materials. Chapter 3 surveys the plate modes in surface acoustic wave devices and the theory needed to understand plate modes in piezoelectric media, as well as to eliminate or reduce their effect on the response. Chapter 4 tackles the ways of predicting diffraction loss and phase distortion, and discusses the alleviation of diffraction effects by acoustic beam shaping, material selection and orientation, and alterations in the transducer structure. Chapter 5 examines plate vibrators whose thickness direction has an arbitrary crystallographic orientation and the tools for the analysis of the properties of doubly rotated cuts, with special emphasis on such cuts in quartz, berlinite, lithium tantalate, and lithium niobate. Chapter 6 discusses generalized ray theory and transient responses of layered elastic solids. This book will be of great value to researchers in the fields of electronics technology and applied and engineering mechanics.