Consonant discrimination using the formant coarticulation model

Formant trajectories in the vicinity of consonants in continuous speech are observed to discriminate the place of articulation of the consonants. The coarticulation model [S. Chiba, Proc. IEEE ICASSP-86, Paper 49-10 (1986)] with a target formant frequency for consonants is developed based on the observation of the formant trajetories in natural VCV utterances. The coarticulation model proposed here is as follows: Fb − Ft = a(Fp − Ft) + b(Fe − Ft) + c(Ff − Ft) + E, where Fb, Fp, Fe, and Ff are the second formant frequencies at the centers and the consonant boundaries of the initial and final vowel segments in a VCV sequence, Ft is the target second formant frequency of the consonant, and E is the estimation error. The parameter values of a, b, c, and Ft are estimated by the method of least squares using actual values. Three coarticulation models for labials, alveolars, and velars are estimated and these models are applied to the discrimination of place of articulation of consonants in continuous speech. Experimental results show that the models for labials and alveolars can estimate the formant trajectories accurately and that a high-discrimination rate of 94% is obtained by comparing prediction trajectories with actual values. In the case of velars, however, the discrimination rate is low.