ABSTRACT

Bulk of recorded sound history the audio information was stored in mechanical media, such as a phonograph record or wax cylinder, via undulated surface incisions (grooves). The grooves’ shape and position can be reconstructed without mechanical contact by using precision optical metrology tools. The surface map thus obtained can be digitally processed further to remove noise artifacts due to damage and wear, and to convert the groove positional information into audio format. The viability of this approach was recently demonstrated on a 78 rpm shellac disc using two dimensional image capture and analysis methods. The present work expands on these results. A three dimensional reconstruction of mechanically recorded sound is reported. The surface of the source material, a wax cylinder, was scanned using co focal microscopy techniques and resulted in a faithful playback of the recorded information. The approach holds promise for careful reconstruction of valuable historical recording using full surface information to improve the sound fidelity, as well as means of automated mass digitization. Fast processing is required for the latter application. Methods to accelerate the scan rates, thereby making these techniques practical for use in working archives, are reported.