Physical Foundations of Technical Acoustics discusses theoretical foundations of acoustical engineering. It is not so much a technical compendium as a systematic statement of physical laws so conceived that technologists might find in it all the information they need to become acquainted with the physical meaning and mathematical expression of phenomena they encounter in their work. To facilitate the acquirement of notions, which lie beyond a layman's grasp, the plan of narration adopted consists in beginning with the simplest idealized cases and then gradually moving on to the truest possible picture of real phenomena. Thus, the first part of the book, dealing with the acoustic field, begins with lossless fluid media, and passes then through perfectly elastic solid media to the real ones, showing losses and relaxations. In the second part, discussing the acoustical systems, the reader is led up from the simplest vibrating system with one degree of freedom to inhomogeneous spatial systems. Classical problems of theoretical acoustics are linked to the questions which appeared still to be the subjects of research. A special chapter has been written to deal with nonlinear acoustics, in consideration of continually growing applications of the acoustic fields of high intensity.