This chapter presents a broad outline of the fundamentals of acoustics, covering the basic principles and concepts that form the foundation of the field. The chapter begins with an introduction to the nature of sound and its propagation, including the fundamental properties of waves and the mechanisms by which sound is generated and transmitted. The chapter then delves into the principles of acoustical measurement, including the various parameters and metrics used to quantify sound and the instruments and techniques used for measurement. The chapter also discusses the behavior of sound in different environments, including the principles of reflection, absorption, and diffraction, as well as the factors affecting the transmission of sound through different media and weak interaction between suspended particles and dispersion medium. Finally, the chapter explores the applications of acoustics in various fields, including music, architecture, and engineering, highlighting the importance of understanding the fundamentals of acoustics in these and other areas. Overall, this chapter serves as a comprehensive introduction to the fundamental principles of acoustics, providing a solid foundation for further study and exploration in the field.