Sound originating outside the visible frame — voices, effects, music without on-screen source. Creates spatial depth and narrative context beyond what we see.
Off-screen audio functions like an invisible hand that expands the visual space. What we don't see, we hear — and that immediately creates spatiality. A car drives by, even though the street remains empty. A voice calls from next door. Music penetrates from outside. These sounds define a space larger than the frame shows, and that is their core task in film.
In practice, we distinguish two functions: narrative off-screen audio — dialogues, thoughts, comments — and spatial off-screen audio, which signals the environment. A voice heard from the left, even though the person is not in frame, automatically draws the viewer's attention to the left — their brain completes the invisible source. This is pure psychoacoustics in service of the narrative. In editing, off-screen audio works as a pre- or post-cue for cuts: the sound of the next scene can already be playing before we cut, or the voice from the old scene lingers briefly. This is called an L-cut or J-cut — both play with the temporal offset between image and sound.
On set, off-screen audio is often undervalued. The boom operator must understand that sounds from the unseen must be placed just as accurately as visible sources — sometimes even more precisely, because localization comes solely from the ear. A sound that sounds too close feels wrong; one that is too far away loses its impact. Control is achieved through distance to the microphone and later through spatial effects — reverb, reflections, frequency limitation — that simulate distance.
Off-screen audio is also a narrative tool. A dialogue between two characters, only one of whom is visible, creates tension and asymmetry. A sound from outside can pull attention or indicate danger before it becomes visible. In horror films, off-screen audio functions as an invisible threat — the unknown is always more disturbing than the known. Therefore, off-screen audio is used not only to save space or disguise cuts, but to create psychological impact.