Optical sound was once the preferred analogue exhibition format for cinema sound before the advent of digital formats. A film projector is equipped with an optical reader that uses light to read whatever may lie along the soundtrack area of the film stock, be it dust, scratches or waveforms.
To create an optical track professionally waveforms generated from sounds are photographically printed onto film negative to be composited with the cinematic image during printing. As the finished soundtrack passes over the optical reader, the waveform is read by light and the signal is converted to physical sound that is projected in concert with the image.
The art of creating 16mm optical tracks is waning professionally, as film is no longer the industry exhibition medium of choice. Its industrial obsolescence impedes traditional workflows but also opens up new possibilities for creative thinking and invention with the medium.
The following is a small sketch from a recent darkroom experiment with Kodak 16mm sound stock, a mirror, an aperture, optics, light and a speaker. Its a first attempt to try and create a rudimentary form of optical sound and a visualization of the corresponding wavelengths. All sound was recorded from an optical reader through an 16mm Eiki projector.
Thanks to Rob Butterworth.