Our lives are full of soundsSound ranging from annoying noise to beautiful musicMusic. The soundSound of speech is an important way we have to communicate. Because of the critical nature of soundSound in our lives it is important that we understand what soundSound is and learn about its physical characteristics. We already know a lot about waves but soundSound waves are very different from light waves. We focusFocus on these differences in this chapter. Some of the themes of the chapter are represented in Fig. 12.1 which shows an airplane creating a sonic boom.