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Variable Area
Variable Density
Video Black
Vinegar Syndrome

Variable Area

From Chace Audio

Variable area, or V/A, refers to the most modern format of analog optical soundtrack recording. It appears as a waveform in the soundtrack area of the film between the perforations and the picture frame. The thickness of the waveform, actually a photograph of a modulating bias line, varies within the soundtrack area, hence the term variable area. The smaller the amount of modulation, the quieter the recorded sound will be, and the larger the modulated area, the louder it will be. V/A soundtracks can be either mono or stereo and have a frequency response of 31Hz to 12.5kHz.

V/A formats have been around since the early to mid 20th century. The first V/A format was “single unilateral,” and consisted of a single bias line modulating outward in one direction only. Then the “dual unilateral” format was introduced, featuring two bias lines modulating in the same direction. The “RCA duplex” format, with two bias lines each modulating inward, was developed next. Later still, the “single bilateral” soundtrack was the first V/A format to utilize modulation from both sides of the bias line. All of these had been mono formats. Finally, the most modern and common V/A format, which can be either mono or stereo, is “dual bilateral” and consists of two bias lines modulating in both directions.

All V/A optical sound tracks are designed to have some form of noise reduction – either Dolby® A, Dolby SR, or the Academy filter for non-Dolby tracks. Non-Dolby optical tracks are EQ'd with Academy pre-emphasis. Without this pre-emphasis, soundtracks sound unnaturally dull when the Academy filter is applied.

The variable area soundtrack on this print can be seen as a pair of squiggly lines to the left of the film frame.