Perspecta

Perspecta was a directional motion picture sound system invented by the laboratories at Fine Sound Inc. in 1954. The company was founded by Mercury Records engineer C. Robert (Bob) Fine, husband of producer Wilma Cozart Fine. As opposed to magnetic stereophonic soundtracks available at the time, Perspecta's benefits were that it did not require a new sound head for the projector and thus was a cheaper alternative.

Introduced as a "directional sound system" rather than a true stereophonic sound system, Perspecta did not use 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 stereophonic sound, which would be described as discrete tracks running in synchronization in time and phase, Perspecta merely panned a mono mix across various channels. Because of this, only isolated dialogue or sound effects could be mixed to be directional. Mixed sound effects, dialogue and music could not be suitably mixed. Aside from panning, Perspecta controlled gain levels for each channel through the amplitude of each control signal.