Mapping palatal shape to electromagnetic articulography data: An approach using 3D scanning and sensor matching.

A method for superimposing the shape of the palate on three-dimensional (3D) electromagnetic articulography (EMA) data is proposed. A biteplate with a dental impression tray and EMA sensors is used to obtain the palatal shape and record the sensor positions. The biteplate is then 3D scanned, and the scanned palate is mapped to the EMA data by matching the sensor positions on the scanned image with those in the EMA readings. The average distance between the mapped palate and the EMA palate traces is roughly 1 mm for nine speakers and is comparable to the measurement error of the EMA.

Replacement of sensor cables for reducing effects on articulation in the Northern Digital Incorporated's Wave electromagnetic articulography system.

This study attempted to improve the five-degrees-of-freedom sensors of the Northern Digital Incorporated's Wave electromagnetic articulography system by replacing their cables with thinner and more flexible cables to reduce interference in articulation. Measurement errors and data loss rates were compared between the original and the proposed sensors. The proposed sensors showed twofold tracking accuracy and data loss rates compared to the original sensors in an experiment using a crank-rocker mechanism. Data loss rates of the proposed sensors increased in articulatory data collection from four speakers. The proposed sensors have been made available commercially.

Visualisation of hypopharyngeal cavities and vocal-tract acoustic modelling.

The hypopharyngeal cavities consist of the laryngeal cavity and bilateral piriform fossa, constituting the bottom part of the vocal tract near the larynx. Visualisation of these cavities with magnetic resonance imaging (MRI) techniques reveals that during speech, the laryngeal cavity takes the form of a long-neck flask and the piriform fossa takes the form of a goblet of varying shapes: the former diminishes greatly in whispering and the latter disappears during deep inhalation. These cavities have been shown to exert significant acoustic effects at higher frequency spectra. In this study, acoustic experiments were conducted for male and female mechanical vocal tracts with the results that acoustic effects of those cavities determine the frequency spectra above 2 kHz, giving rise to peaks and zeros. An acoustic model of vowel production was proposed with three components: voice source, hypopharyngeal cavities and vocal tract proper, which provides effective means in controlling voice quality and expressing individual vocal characteristics.