This document defines various types of diegetic and non-diegetic sound used in films. It discusses diegetic sound that exists within the scene's world and non-diegetic sound that does not. It also defines synchronous and asynchronous sound, parallel and contrapuntal sound, ambient sound, sound bridges, and sound motifs. Finally, it discusses the concept of verisimilitude, which is creating believability in a story through realistic details like sound. An example given is the sounds used in Saving Private Ryan to make the scenes as realistic as possible.