Place of articulation from direct imaging for validation of its estimation from speech analysis for use in speech training

Place of articulation obtained by analysis of the speech signal is useful for visual feedback of articulatory efforts for speech training of hearing impaired children and for improving pronunciation by learners of second languages. Its estimation by direct imaging of the oral cavity is needed for validating the estimation from the speech signal. For such applications, an automated technique is presented for estimating the place of articulation by graphical processing of the upper and lower contours of the oral cavity image. It iteratively estimates the axial curve as an axis of symmetry of the oral cavity, such that the curve approximately bisects the normals to it. Distance between the contours along the normal to the axial curve gives the oral cavity opening and position of the smallest opening provides the place of articulation. The values estimated using the automated technique closely matched those obtained by manual marking of the visually estimated place of maximum constriction for the oral cavity images of vowels, stops, and fricatives, from the XRMB and MRI databases.