The term derives from the Greek “akouw,” for “hearing” (as opposed to deaf) and a range of associated meanings: to hear, to listen or attend to something heard, to understand (in particular, what was heard), to learn (through listening), and even to obey ( a word itself arising from the Latin “audire,” to hear, as if the open ear canal were a conduit for suggestion and the implantation of the desires of others, to which there could be no resistance). It was first applied to the disembodied voice of the classical Greek mathematician and philosopher Pythagoras, as he required his students to listen to his teaching from behind a curtain so that they would not be distracted by his appearance, a usage that resonates with the arguments by film and media theorists that the embodied voice is experienced as partial and limited, rather than authoritative and commanding; hence the source of the classic documentary voice-over is never revealed (and gods too must not be seen but heard). As defined by French film scholar Michel Chion, who borrowed the term from Pierre Schaeffer (a French composer, engineer, and musicologist), acousmatic sound differs from visualized sound because it lacks a clear source in the image (for Schaeffer, it referred to a media-saturated culture whose sound sources are not readily apparent). It evokes anxiety because it seems omnipotent, omniscient, and omnipresent. All offscreen sound is therefore acousmatic, and the diegetic world of narrative film is extended beyond the bounds of the frame by visualizing sounds first heard through cinematography or editing that finally locate them onscreen, revealing their source.
The reverse is also true: visualized sound can be acousmatized in shots that succeed those in which it was introduced and assigned an origin, bridging space (and time). Sound, in particular, sync sound, which is visualized sound, thus contributes to the effect of realism in film, while acousmatic sounds introduce a spectral, uncanny dimension to an otherwise realist diegetic world, which is why they are an important element of gothic and horror films (by contrast, the loss of sync disrupts filmic realism and seems to mock the speaker or singer whose voice floats free of his or her body and apparent control). Media involving the telepresence of a voice unanchored from its speaker, such as the telephone, phonograph, and radio, have been experienced as weird and ghostly when first introduced, and hearing one’s own voice on an answering machine or other recording device still produces a similarly unsettling sensation, as one does not sound like oneself when air alone is the primary transducer of sounds typically conducted through bone and soft tissue at the same time. The voice as theorized by psychoanalyst Jacques Lacan is always acousmatic, only loosely articulated with the body from which it emanates, since the desire and the language to which it gives rise comes from the Other. Voice as the vehicle of authentic self-expression, as in feminist, ethnic nationalist, and other “New Left” social movement discourses is for him largely an illusion, since the voice is always alien and alienating. For Lacan, voice belongs first and foremost to the Other as the cause of desire, an unattainable object around which the “invocatory drive” endlessly circles, as the subject tries to sustain a distance from and pacify the siren call that might be its undoing.