concept

Non-diegetic sound

Sound the story world cannot account for. Three textbooks draw the line in three places, and the edge cases are where films work.

audio
film-language

A sub-concept of the Audio code. Diegetic sound belongs to the story world; non-diegetic sound belongs to the telling. Score is the obvious case, and because no character can hear it, it is the one channel on which a film addresses its audience with no narrative alibi at all. The definition looks trivial. It is not, because the test you use to draw the line decides the hard cases, and the hard cases (voice-over, a thought heard as speech, a score that quotes another film) are where the channel does its most interesting work. The mistake students make is treating "non-diegetic" as a label to apply. Treat it instead as a question the film is asking: who is this sound for?

Three tests

Bordwell and Thompson test by source. Diegetic sound "has a source in the story world"; non-diegetic sound "is represented as coming from a source outside the story world". The test lets them keep a third category, internal diegetic sound, for a thought we hear but nobody in the scene does: "Does the sound come from inside the mind of the character? That is also diegetic". Giannetti tests by audibility: "sounds that the characters can hear as diegetic, while sounds they can't hear are nondiegetic". That is easier to teach and fails at once on a soliloquy, which only its speaker hears. Hayward tests by the screen: non-diegetic sound is "not being produced within the on-screen space", and she adds the theorist's reminder that the whole distinction is a convention, since "even diegetic sound and space are totally illusory and falsely constructed".

The difference matters. Giannetti's test has trouble with Travis Bickle's diary voice-over: nobody in the cab hears it, so it reads as a narrator's voice. Under Bordwell and Thompson it is internal diegetic: the source is the man in the cab. The second reading is the useful one, because it keeps the film inside Travis's head rather than granting him an outside commentator. Hayward's contribution is the reverse case, the extra-diegetic sound that arrives "with no logical reason for being there" and reminds the viewer that a film is a made thing.

On the bench

Psycho — the shower scene is the channel measured. Hitchcock asked for the murder to play unscored; Herrmann wrote the strings anyway and Hitchcock conceded on hearing them (Herrmann scored the shower against orders). Bordwell and Thompson catch what the cue does: "when a woman screams, we expect to hear a voice but instead hear violins". The non-diegetic sound takes over a diegetic job, and the violence roughly doubles.

Taxi Driver — the shoot-out closes on a quotation of Herrmann's own Psycho score, so the coda that looks like recovery is heard as diagnosis (Herrmann finished the score and died that night). This is non-diegetic sound as citation: a channel no character hears, carrying a reference no character could know. The Craft — light as a feather approaches the same question from the other side. There is no cue at all; four voices chanting inside the scene do what a score would normally do, and the cutting locks to their beat (The chant is a metronome, not a spell). A diegetic sound performing the non-diegetic function is the best test of whether a student understands the distinction rather than the label.

Mean Streets (1973) is the test case from the other side: a film that almost never crosses the line. Its music comes from sources in the story world, a model Scorsese took from The Public Enemy (The jukebox is the score). The exception is his own voice, which speaks Charlie's thoughts from outside the fiction (Mean Streets — the opening).

What to look for

Apply all three tests to one sound. Where do they disagree, and which answer does the film seem to want?
If a character narrates, is the voice inside the story (a diary, a memory) or outside it (a commentator)? What would change if it were the other?
When music starts, could a character in the scene have started it? When it stops, who stopped it?
Does the score ever quote something the audience knows and the characters do not?

In the books

Alternatively, there is nondiegetic sound, which is represented as coming from a source outside the story world.

— Film Art, fa 285

Does the sound come from inside the mind of the character? That is also diegetic, but rather internal diegetic sound.

— Film Art, fa 291

Critics refer to sounds that the characters can hear as diegetic, while sounds they can't hear are nondiegetic.

— Giannetti, um 200

The term non-diegetic sound refers to sound that clearly is not being produced within the on-screen space (such as voice-over or added music).

— Hayward, ckc 111

Deepest on this in the library

Measured across the 72 books indexed in Reel — how much denser each one is on this concept than the library average. A place to read next, not a claim about quality.

11.6× Donna Kornhaber — Wes Anderson 24 passages · cite as wak
4.6× Per Persson — Understanding Cinema 18 passages · cite as uc
4× Susan Hayward — Cinema Studies: The Key Concepts 35 passages · cite as ckc
3.8× Ed Sikov — Film Studies: An Introduction 16 passages · cite as sik
3.8× Barsam & Monahan — Looking at Movies: An Introduction to Film 41 passages · cite as lam
3.1× Pramaggiore & Wallis — Film: A Critical Introduction 47 passages · cite as fci

Go on, then

scene Alice — the prologue Ninety seconds of counterfeit 1940s Hollywood, built at real 1940s expense, existing to be destroyed by one cut.
film Alice Doesn't Live Here Anymore (1974) Scorsese's studio women's picture: a widow, a kid, a road east, and an argument with every film Alice grew up watching.
idea Herrmann finished the score and died that night Bernard Herrmann took some persuading to score a film with a title he disliked. He completed it on Christmas Eve 1975 and died the same night.
idea Herrmann scored the shower against orders Hitchcock asked for the murder to play unscored. Herrmann wrote the strings anyway, and Hitchcock conceded on the spot.
scene Mean Streets — the opening A voice in the dark, a man who cannot stay asleep, and a Ronettes record that lands on the downbeat as his head hits the pillow. The film's argument and its method before the first title.
scene Mean Streets — Tony's bar Charlie walks into a room lit like hell in slow motion; later Johnny Boy walks in on the downbeat of 'Jumpin' Jack Flash' with a girl on each arm. Two entrances, one room, and the camera's opinion of both.