Book excerpt: The interaction of sound waves with the medium through which they pass can be used to investigate the thermophysical properties of that medium. With the advent of modern instrumentation, it is now possible to determine the speed and absorption of sound with extremely high precision and, through the dependence of those quantities on variables like temperature, pressure, and frequency to gain a sensitive measure of one or more properties of fluid. This has led to renewed interest in such measurements and in the extraction of thermophysical properties of gases and liquids there from. Physical Acoustics and Metrology of Fluids describes both how to design experiments to achieve the highest possible accuracy and how to relate the quantities measured in those experiments to the thermophysical properties of the medium. A thorough theoretical examination of the alternative experimental methods available is designed to guide the experimentalist toward better and more accurate methods. This theoretical analysis is enhanced and complemented by an in-depth discussion of practical experimental techniques and the problems inherent within them. Bringing together the fields of thermodynamics, kinetic theory, fluid mechanics, and theoretical acoustics, plus a wealth of information about practical instruments, this book represents an essential reference on the design and execution of valuable experiments in fluid metrology and physical acoustics.