Accurate yet imaginative audio is part of what creates truly immersive film and TV. Dialogue, music, and sound effects work synergistically to legitimize a sense of filmic reality, set mood, and establish tone. From the avian cries in “The Birds,” to the omniscient narration in “Amélie,” sound in film and TV is either diegetic, non-diegetic, or a mix of the two. Keep reading to learn about the differences between these sound sources and examples of both onscreen.
Diegetic sound is sound that can be heard by characters in a film or TV show. The word diegetic comes from “diegesis,” or a style of storytelling based on a character’s interior narration.
Whether it’s characters dancing to a song at a wedding or witnessing the metal clanging of an offscreen car crash, if the sound is created by and fits within the narrative world of a film or TV show, it’s diegetic.
For example, in this scene from “The Office,” the characters clearly hear when the song changes from wedding organ music to “Forever”—as evidenced by their sweet dance moves and high kicks.
The main types of diegetic sound are:
Dialogue: When two characters speak out loud to each other, the sound source is in-film. Dialogue usually conveys something about character personalities and how they interact with one another.
Music that characters can hear: This may be music that is made in the film and heard by the characters, like a band performing or a violinist playing their instrument; or it could be a karaoke scene—such as when bride-to-be Kimmy Wallace awkwardly yet charmingly sings “I Just Don’t Know What to Do With Myself” in “My Best Friend’s Wedding.”
Object sounds: Object sounds that happen in a scene, such as a horse clopping down the street during Big and Carrie’s buggy ride through Central Park in “Sex and the City,” are diegetic.
Although diegetic sound happens within the fictional world of the story, it might not have been recorded on set. Productions often use automated dialogue replacement (ADR), or looping, to improve or change dialogue in postproduction. Similarly, many projects add foley sound effects after shooting has wrapped to enhance audio quality. These sounds add to a film’s realism and believability, help draw viewers in, and legitimize quiet scenes by adding ambient sounds.
Non-diegetic sound is any sound that does not come from within the film’s world and that characters cannot hear. These sounds are nearly always added in postproduction.
For example, the opening scenes for the “Star Wars” series use non-diegetic music from composer John Williams to create a highly accessible sci-fi experience for the audience.
The main types of non-diegetic sounds are:
Soundtrack and score: The incidental music of a film, used to create atmosphere or otherwise set tone, is audible to the audience but not the characters.
For example, Disasterpeace’s chaotic, synth-based soundtrack in “It Follows” alerts the audience to the violent disruption of the creature stalking the protagonist, Jay—but she doesn’t hear it.
Some sound effects: Effects clearly not heard by characters within a fictional world are sometimes used for exaggerated effect. For example, a “ding” sound accompanies every wink from Barney Stinson in this montage from “How I Met Your Mother.”
Voiceover narration: Voiceover audio is usually recorded off-camera and added into the project in postproduction. Except for the times narration breaks the fourth wall—such as the villain hearing narrator Keith Scott’s sonorous intonations in “George of the Jungle”—it is usually non-diegetic.
For example, Alec Baldwin narrates the world of “The Royal Tenenbaums,” offering insight into the family and their various escapades.
When a film combines diegetic and non-diegetic sound, they become trans-diegetic. Mixing both sound types is ideal for creative storytelling and for transitioning between scenes without being overly abrupt or disruptive. Trans-diegetic sound, such as a sound from the score becoming a song heard on the radio in a film, creates a seamless link between scenes that helps the audience acclimate to the world of the movie.
For example, the opening of “Dog Day Afternoon” sees the Elton John song “Amoreena” playing over a montage of New York City (non-diegetic), before cutting to reveal that the song is coming from a character’s car radio (diegetic).
Diegetic, non-diegetic, and trans-diegetic sound all contribute to the overall sound design of a film, which lends itself to atmospheric sonic and cinematic experiences.