What defines 'diegetic sound' in media?

Diegetic sound is defined as sound that originates from within the film's world, which means both the characters and the audience can hear it. This type of sound includes dialogue between characters, sounds made by objects in the scene, and music played by instruments present within the narrative. By definition, diegetic sound helps to establish the environment and contribute to the audience's immersion in the story, as it reflects the reality of the characters' experiences.

In contrast to this concept, sounds only heard by the audience would be referred to as non-diegetic sound, reflecting music or voiceovers that do not exist in the film's world. Music that enhances the film's mood is also classified as non-diegetic as it serves a narrative purpose but is not part of the characters' reality. Similarly, sound effects added in post-production can be either diegetic or non-diegetic but do not specifically define diegetic sound unless they are sounds that the characters themselves can hear and react to in the scene.