This book is intended to introduce the fundamentals of acoustic wave motion, and the topics covered by the book include duct acoustics, sound in enclosures, and sound radiation and scattering. Some of the most difficult parts of acoustics for beginners, such as the widely different approximations due to the wide frequency range, the apparently arbitrary choice between the use of analytical solutions to the wave equation with boundary conditions and the fundamentally different energy-based considerations used in noise control are not sufficiently well explained in many textbooks. This book will address these issues in a clear and systematic way in order to provide readers with a self-contained source of information on acoustics.