Part I should provide the basic knowledge of underwater acoustics that is needed for the remaining part of the book. Although the word acoustics was originally associated with the sound properties of rooms, its usage is here broadened to include wave phenomena in media other than air, and frequencies other than those audible to the human ear.

The first chapter summarizes the notations and basic concepts of underwater sound with a bias towards the needs of the remaining chapters. The purpose of the second chapter is twofold, namely to introduce the sounds of interest, i.e. the sounds made by different cetaceans, and to develop techniques that are suited to describing the different sound categories. The third chapter presents and discusses all the components of the sonar equation, which is the workhorse of sonar design and performance analysis; I focus on the passive sonar equation, which is the version that is relevant for PAM.