Pronouncibility index (Π): a distance-based and confusion-based speech quality measure for dysarthric speakers

摘要

Recently, there have been many modern speech technologies, including those of speech synthesis and recognition, developed to help people with disabilities. While most of such technologies have successfully been applied to process speech of normal speakers, they may not be effective for speakers with speech disorder, depending on their severity. This paper proposes an automated method to preliminarily assess the ability of a speaker in pronouncing a word. Based on signal features, an indicator called pronouncibility index (Π) is introduced to express speech quality with two complementary measures, called distance-based and confusion-based factors. In the distance-based factor, the 1-norm, 2-norm and 3-norm distance are investigated while boundary-based and Gaussian-based approaches are introduced for confusion-based factors. The Π is used to estimate performance of speech recognition when it is applied to recognize speech of a dysarthric speaker. Three measures are applied to evaluate the effectiveness of Π, rank-order inconsistency, correlation coefficient, and root-mean-square of difference. The evaluations had been done by comparing its predicted recognition rates with ones predicted by the standard methods called the articulatory and intelligibility tests based on the two recognition systems (HMM and ANN). For the phoneme-test set (the training set), Π outperforms the articulatory and intelligibility tests in all three evaluations. The performance of Π decreases for the device-control set (the test set), and the intelligibility test becomes the best method followed by Π and the articulatory test. In general, Π is a promising indicator for predicting recognition rate with comparison to the standard assessments.