How to stretch and shrink vowel systems: results from a vowel normalization procedure.

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.