Reconstruction of mechanically recorded sound by image processing

Audio information stored in the undulations of grooves in a medium such as a phonograph record or cylinder may be reconstructed, without contact, by measuring the groove shape using precision optical metrology methods and digital image processing. In this approach, audio signal processing is accomplished by two‐ or three‐dimensional image analysis and processing. The viability of these methods was recently demonstrated on a 78 rpm shellac disc using two‐dimensional image acquisition and analysis methods [V. Fadeyev and C. Haber, J. Audio Eng. Soc. 51(12), 1172–1185 (2003)]. The present work expands on these results. A three‐dimensional reconstruction of mechanically recorded sound is reported. The source material, an Edison cylinder, was scanned using confocal microscopy and resulted in a faithful playback of the recorded information. Methods to accelerate the scan rates and make these techniques practical for use in working archives are reported as well. [Work supported by the Laboratory Technology Research Program (SC‐32), within the Office of Science, U.S. Department of Energy under Contract No. DE‐AC03‐76SF00098.]