In this book, acoustic waves have been described comprehensively. The concept of acoustic wave is an extensive one; it materializes in a variety of mediums, from solids to plasmas, and at varying length and time scales which range from sub-micrometric layers in microdevices to seismic waves in the Sun's interior. This book discusses various approaches of the active research going on in this field. Theoretical attempts lead to a comprehensive understanding of this phenomenon. Such waves are useful in exploring the characteristics of a variety of structures, be it inorganic layers or other bio-structures. These waves can also function as a tool to influence matter, from the gentle evaporation of bio-molecules to be evaluated, to the phase conversions inferred by intense shock waves. Furthermore, a whole class of widespread micro tools, inclusive of filters and sensors, depends upon the behavior of these waves propagating in fine layers.