Suitability of minidisc (MD) recordings for voice perturbation analysis

A new digital recording format, Minidisc (MD), shows promise for high-quality voice recordings. It is available in a portable size and uses magneto-optical recording techniques on a miniature compact disc. The disc can be recorded an unlimited number of times with essentially the same playback life span: however, the digital recording technique uses a data compression algorithm that may interfere with acoustic voice perturbation analysis. This study investigated what effects this compression may have and whether the MD format is viable for use in this application. The MD format was evaluated by traditional synthetic test signals used on recording devices. In addition, human phonation recorded on Digital Audio Tape (DAT) was used as the input to the MD. The output of the MD was then compared to the original DAT recording. The two signals were analyzed for long- and short-term perturbation measures, and their waveforms were visually inspected. The results indicated that the MD format performed as well as the DAT format in all areas of standard tests, with the exception of signal-to-noise (S/N) ratio. S/N ratio for the MD was approximately 10 dB less than for the DAT under normal operating conditions; however, in comparing perturbation measures on normal human vowels, there were no significant differences between the two formats, i.e., no distortions in voice perturbation were introduced by the MD record/playback process.