A Simplified Vocal Profile Analysis Protocol for the Assessment of Voice Quality and Speaker Similarity

A simplified perceptual protocol for the assessment of voice quality (VQ) is attempted based on the Vocal Profile Analysis (VPA) scheme, with the aim of alleviating typical issues associated with the multidimensionality of VQ and enabling an easy quantification of speaker similarity.

Twenty-four non-pathological male speakers (12 monozygotic twin pairs) of Standard Peninsular Spanish were perceptually evaluated by two trained phoneticians using the simplified VPA (SVPA). Based on their perceptual ratings, intra- and inter-rater agreement was measured, and an index of speaker similarity was calculated not only between twin pairs but also between non-twin pairs. For that purpose, one member of each twin pair was compared with a member of a different twin pair.

Intra- and inter-rater agreement measures were tested with unweighted and linear weighted kappa. Speaker similarity was measured with simple matching coefficients (SMC).

The results show that analysts' internal consistency was very high, whereas inter-rater agreement was found to be strongly setting-dependent. SMCs between speakers indicate that twin pairs are, on average, more similar than non-twin pairs.

Agreement results suggest that the proposed SVPA is a reliable protocol for the perceptual characterization of VQ, and SMC results confirm that it can also be a useful tool for the assessment of speaker (dis)similarity. The extraction of a voice quality similarity index shows potential in fields like forensic phonetics, but could also be of interest in related areas of voice research and professional practice.