Absorption and Dispersion of Ultrasonic Waves focuses on the influence of ultrasonics on molecular processes in liquids and gases, including hydrodynamics, energy exchange, and chemical reactions. The book first offers information on the Stokes-Navier equations of hydrodynamics, as well as equations of motion, viscosity, formal introduction of volume viscosity, and linearized wave equation for a nonviscous fluid. The manuscript then ponders on energy exchange between internal and external degrees of freedom as relaxation phenomenon; effect of slow energy exchange on sound propagation; different ways of evaluating the dispersion curve; and exact calculation of absorption and dispersion. The text examines the effects of chemical reactions, thermodynamic theory of relaxation, and mixtures. The book also evaluates the absorption of high intensity sound waves, ratio of relaxation absorption to classical absorption at maximum, and gas mixtures. Discussions also focus on translational relaxation in monatomic gases, linear triatomic molecules, and results for rotational relaxation. The manuscript is a dependable source of data for readers interested in the absorption and dispersion of ultrasonic waves.