Chapter 5 discussed how sound waves are transmitted under the assumption that sound travels from one point to another. This explanation involved a one-dimensional transmission, as it only considered sound waves traveling in one direction. However, most sounds that humans hear on a daily basis are not transmitted through such a simple process, as most sounds go through a complex process to reach the human ears, in which sound waves reverberate off surfaces, panels, or within a space. Then, how is sound transmitted through surfaces, panels, or spaces? This chapter discusses the sound transmission process across surfaces, panels, and spaces.