Perspecta

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Perspecta was a format of "fake" motion picture stereophonic sound, invented by the laboratories at Fine Sound Inc. in 1954. It was a competitor at the time that it was introduced to magnetic stereophonic tracks for motion pictures. Its benefits were that it did not require a new sound head for the projector and thus was a cheaper alternative.

Perspecta was a faux-stereo system in that it did not utilize discretely recorded sound signals. Instead, three sub-audible tones at 30 Hz, 35 Hz, and 40 Hz are mixed appropriately and embedded in a monaural, optical soundtrack, in addition to the audible sound. When run through a Perspecta integrator, depending on whenever each tone is present, the audio is fed into a left (30 Hz), center (35 Hz) and right (40 Hz) speaker. Unlike true stereo, in which each voice and/or sound effect moves individually in the same direction (s) as the actor(s) moved and spoke onscreen, in Perspecta, all sounds and voices could only move simultaneously. Because of this, only sound effects could be heard in what sounded like true stereo, and only when no speech or music was heard along with them. Aside from panning, Perspecta controlled gain levels for each channel through the amplitude of each control signal.

Paramount Pictures was a major supporter of Perspecta when they introduced their VistaVision motion picture system that same year. Subsequently, all VistaVision films carried Perspecta tracks, until it fell out of favor around 1958. Universal-International, United Artists, MGM Studios and Toho were among some of the other major studios to utilize Perspecta regularly.