Volume 125, Issue 5, May 2009
Index of content:
- SPEECH PRODUCTION 
125(2009); http://dx.doi.org/10.1121/1.3106130View Description Hide Description
One of the goals of phonetic investigations is to find strategies for vowel production independent of speaker-specific vocal-tract anatomies and individual biomechanical properties. In this study techniques for speaker normalization that are derived from Procrustes methods were applied to acoustic and articulatory data. More precisely, data consist of the first two formants and EMMA fleshpoint markers of stressed and unstressed vowels of German from seven speakers in the consonantal context /t/. Main results indicate that (a) for the articulatory data, the normalization can be related to anatomical properties (palate shapes), (b) the recovery of phonemic identity is of comparable quality for acoustic and articulatory data, (c) the procedure outperforms the Lobanov transform in the acoustic domain in terms of phoneme recovery, and (d) this advantage comes at the cost of partly also changing ellipse orientations, which is in accordance with the formulation of the algorithms.
Closed phase covariance analysis based on constrained linear prediction for glottal inverse filtering125(2009); http://dx.doi.org/10.1121/1.3095801View Description Hide Description
Closed phase (CP) covariance analysis is a widely used glottal inverse filtering method based on the estimation of the vocal tract during the glottal CP. Since the length of the CP is typically short, the vocal tract computation with linear prediction (LP) is vulnerable to the covariance frame position. The present study proposes modification of the CP algorithm based on two issues. First, and most importantly, the computation of the vocal tractmodel is changed from the one used in the conventional LP into a form where a constraint is imposed on the dc gain of the inverse filter in the filter optimization. With this constraint, LP analysis is more prone to give vocal tractmodels that are justified by the source-filter theory; that is, they show complex conjugate roots in the formant regions rather than unrealistic resonances at low frequencies. Second, the new CP method utilizes a minimum phase inverse filter. The method was evaluated using synthetic vowels produced by physical modeling and natural speech. The results show that the algorithm improves the performance of the CP-type inverse filtering and its robustness with respect to the covariance frame position.