[Show abstract][Hide abstract] ABSTRACT: 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.
Computer Methods in Biomechanics and Biomedical Engineering 08/2010; 13(4):443-53. · 1.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The tongue possesses a complex muscular structure, and its motor functions are also intricate. Therefore, it would be beneficial to use a computational physiological model of the tongue to examine its vital functions in normal and pathological conditions. Thus far, the studies of tongue models have focused on symmetric movements for normal speech. For clinical purposes, it is necessary to develop a physiological model to deal with daily vital activities such as mastication and swallowing. To do so, we constructed a full 3D physiological model of the tongue based on MRI data from a normal subject, and verified the basic functions of the model based on anatomic and physiological knowledge. In this study, the model was applied to clinical issues: prediction and verification of the changes in movements of the tongue with a tumor before and after partial glossectomy, respectively. Tongue protrusion and lateral bending motion were examined for the prediction and verification. The simulation results were consistent with the observations for a patient with a tumor in the tongue. Comparisons of the simulation and observation in the clinical case showed that the model could predict potential effects of the glossectomy on the tongue movements. It is suggested that the model is a useful tool for pre-operative planning of glossectomy.
International Journal of Oral Science 11/2007; 4(2):97–109. · 2.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To develop a physiological articulatory model for speech production, mastication and swallowing, we proposed an analysis-by-synthesis (AbS) based estimation method for investigating contributions of the tongue muscles in both exterior movement and interior deformation using observations and model simulations. The validity of the method was confirmed by comparing the estimated muscle activation to known muscle activation via model simulation using a full three dimensional physiological articulatory model. Observations were conducted to measure several simple tasks of large-scale tongue deformations using tagged magnetic resonance imaging (tMRI), and the principal strain of the deformations were analyzed using HARP MRI analysis. The muscle activation was examined based on the principal strain pattern and anatomic knowledge. According to the observation, a muscle activation pattern was designed to generate a tongue movement with extreme protrusion-retraction using the model. Muscle activation in the movement was estimated by comparing the principal strain pattern and known muscle forces. The model simulation and tMRI observation showed consistent strain patterns with each other. Thestudy showed that the muscle activation within tongue movement is able to be estimated from local deformationsusing the AbS method.
[Show abstract][Hide abstract] ABSTRACT: Simulation techniques using 2D or 3D tongue models have been adopted in investigating mechanisms of speech production. However, large asymmetric deformations of the tongue have not been challenged yet for both normal and pathologic cases. In this study, a full 3D tongue model was constructed by extending an existing partial 3D model, and it is used to perform large asymmetric 3D deformations to generate tongue gestures with bending and torsion. Furthermore, simulations of a hemi-laterally reconstructed tongue demonstrated tongue protrusion with a bending motion, as often observed in real pathological cases. These results confirmed that the proposed tongue model performed behaviors of normal and pathological tongues and that this model can be a useful tool for the study of speech disorders with pathology of the tongue.
[Show abstract][Hide abstract] ABSTRACT: This work proposes an experimental method for direct measurement of transfer functions of acoustic tubes. The method obtains a pressure-to-velocity transfer function from measurement of input volume velocity and output pressures of a target tube. Steady sinusoidal waves from 100 Hz to 5 kHz with a 10-Hz increment were used as a source signal. Experimental results compared with transmission line simu- lations indicate the following: (1) transfer functions obtained from the measurements agree well with those from transmis- sion line simulations; (2) differences between the resonant frequenciesobtained fromthe measurementsand simulations with a uniform tube are less than 2.6 %. These results show conclusive evidence that the proposed method permits accu- rate measurements of transfer functions of acoustic tubes.
INTERSPEECH 2004 - ICSLP, 8th International Conference on Spoken Language Processing, Jeju Island, Korea, October 4-8, 2004; 01/2004