Physical Acoustics: Principles and Methods reviews the principles and methods of physical acoustics and covers topics ranging from third sound in superfluid helium films to the method of matched asymptotic expansions (MAE). Ultrasonic diffraction from single apertures and its application to pulse measurements and crystal physics are also discussed, together with elastic surface wave devices, acoustic emission, and nonlinear effects in piezoelectric quartz crystals. Comprised of six chapters, this volume begins with a detailed treatment of the theory of third sound in superfluid helium films, third sound resonators, and many other properties. The second chapter is devoted to the MAE method, with emphasis on its ability to produce results in acoustics and to provide insight into classical problems. Subsequent chapters deal with bulk and surface waves; phase coded signals and their generation and detection by interdigital grid structures; elastic surface wave devices such as pulse compression filters; and nonlinear effects in quartz crystals. The final chapter describes acoustic emission and the noise produced in materials when they are strained. This book will be of interest to physicists.