Perceptual tests and feature extraction: Toward a novel methodology for the assessment of the digitization of old ethnic music records

The importance of preserving and ensuring access to the ethnic music heritage is now widely recognized. Almost the entire audio archive community agrees on the fact that the only practicable way to preserve this heritage is the re-recording of old analogic documents in the digital domain. Despite this, the strategies to optimize the extraction of the audio signal from the original carrier is still an open issue. An experiment was carried out to evaluate the influence of the stylus in the re-recording of old phonographic records. A disc of ethnic music was digitized several times, using four styli that differ in shape and size: a truncated elliptical of 3.0mil, a truncated elliptical of 2.5mil, a truncated conical of 1.1mil and a stereo stylus. The four different versions were evaluated by 24 subjects and were analyzed by means of signal analysis and feature extraction algorithms. The data show a significative relationship among the stylus type and the perceptual quality, allowing a better understanding of which are the relevant acoustic features and how they influence the quality of the re-recording.