Individual Passaggio Identification Based on Laryngeal Surface Vibration Ratios Measured by Laser Doppler Vibrometer

Passaggio is a natural physiological phenomenon during vocal register transitions in singing, with its pitch location varying across individuals. Conventional identification methods rely on auditory judgment or voice type classification, which may be limited in accuracy due to individual differences. This study proposes a method for estimating individual passaggio intervals based on laryngeal surface vibration measured by a laser Doppler vibrometer (LDV). In this study, laryngeal surface vibration signals and singing voice signals were synchronously recorded from 20 trained singers using an LDV and a microphone. The results indicate that passaggio intervals can be estimated from the variation in the ratio between the first two dominant low-order peaks (L0/L1) in the laryngeal vibration spectrum. In blind perceptual validation, 71.67% of expert judgments fell within the estimated intervals and 96.67% within ±2 semitones. Comparison with reported pedagogical passaggio ranges (e.g., Miller) showed a 75% overlap, reaching 90% in male singers. These findings suggest that the LDV-based method for passaggio identification may provide a promising non-invasive approach for estimating individual passaggio intervals. However, as an exploratory study, further validation is required.