Reconstruction of Recorded Sound from an Edison Cylinder using Three-Dimensional Non-Contact Optical Surface Metrology

Audio information stored in the undulations of a groove in a mechanical sound carrier such as a cylinder or disc phonograph record may be reconstructed, without contact, by measuring the groove shape using precision optical metrology methods and digital image-processing. The viability of this approach was recently demonstrated on a 78r.p.m. shellac disc using two-dimensional image acquisition and analysis methods. The present work reports the first three-dimensional reconstruction of recorded sound from a mechanical carrier. The source material, a celluloid cylinder, was scanned using colorcoded confocal microscopy techniques and resulted in a faithful playback of the recorded information.