Book excerpt: Physical and Applied Acoustics: An Introduction explores the mechanical-acoustical or acoustical-electrical analogies that are based on common theoretical relationships. This book is composed of 11 chapters that discuss the theory, experiment, and technological applications of physical and applied acoustics. The introductory chapters deal with the sound wave propagation in liquids and gases, as well as the statistical theory of room acoustics. These topics are followed by discussions on sound absorption in different medium; the concept of sound radiation pressure; directional characteristics of sound sources; measurement and calibration of acoustics; and the fundamental physical and psychological facts of acoustics. The subsequent chapters cover the use of electroacoustics for the transmission of speech and music. A chapter examines the production and detection of extremely high-frequency sound, called quantum acoustics. The concluding chapter highlights the interaction phenomena between sound and flow in a medium.