The acoustic propagation in the human vocal tract using the Transmission Line Matrix method (TLM) has been simulated. Tri-dimensional meshes are built from segmented magnetic resonance images. Initially, simple models of one and two tubes were constructed to then simulate the same signal in a human vocal tract model whose shape represents the production of the open vowel /a/, simulating at the same time a human glottal signal. For the vocal tract model, the voice signals generated by the simulations were compared with voice samples from the same subject from whom the mesh was extracted. A compensation factor for the topology-dependent numerical dispersion for improving formant determination is proposed. It is concluded that the proposed compensation factor improves the effectiveness and accuracy of the TLV method.

Se ha simulado la propagación acústica en el tracto vocal humano usando el Método de La Línea de Transmisión (TLM). Se construyeron mallas tridimensionales a partir de segmentaciones de imágenes de resonancia magnética. Inicialmente se construyen modelos simples de uno y dos tubos y luego se simula la misma señal en un modelo de tracto vocal humano cuya forma representa la producción de la vocal abierta /a/, simulando también la propagación de una señal glotal. Para el modelo del tracto vocal, las señales de voz generadas mediante las simulaciones fueron comparadas con muestras de voz del mismo sujeto a quien se extrajo la malla. Se propone un factor de compensación de la dispersión numérica dependiente de la topología para mejorar la determinación de los formantes. Se concluye que el factor de compensación mejora la eficacia y exactitud del método TLM.

In mechanical system modeling, uncertainties are present and, to improve the predictability of the models, they should be taken into account. This work discusses uncertainties present in boundary conditions using the model of a vibrating Timoshenko beam, free in one end and pinned with rotation constrained by a linear elastic torsional spring in the other end. The Finite Element Method is used to discretize the system and two probabilistic approaches are considered to model the uncertainties: (1) the stiffness of the torsional spring is taken as uncertain and a random variable is associated to it (parametric probabilistic approach); (2) the whole stiffness matrix is considered as uncertain and a probabilistic model is constructed for the associated random matrix (nonparametric probabilistic approach). In both approaches, the probability density functions are deduced from the Maximum Entropy Principle. In the first approach only the uncertainty of a parameter is taken into account, and in the second approach, the uncertainties of the model are taken into account, globally. Both approaches are compared and their capability to improve the predictability of the system response is discussed.

The process of voiced sounds production can be described as follows: air coming from the lungs is forced through the narrow space between the two vocal folds, which are set in motion in a frequency governed by the tension of their tissues. The vocal folds change the continuous flow that comes from the lungs into a series of pulses. Then, as the flow passes through the oral and nasal cavities it is amplified and changed until it is finally radiated from the mouth. This complex process can be modeled by a system of integral-differential equations. In spite of such complexity, this paper shows that it is possible to obtain synthetic voice sounds of satisfactory realism using simple mathematical models. The perception of a synthetic sound as natural is increased by choosing suitable waveforms for the time-varying subglottal pressure, rather than by augmenting the number of degrees of freedom of the mechanical model. This paper also shows possible ways to adapt the models to voices of men, women and children.

In general the motion of a body takes place in a confined environment and collision of the body with the containing wall is possible. In order to predict the dynamics of a body in this condition one must know what happens in a collision. Therefore, the problem is: if one knows the pre-collision dynamics of the body and the properties of the body and the wall one wants to predict the post-collision dynamics. This problem is quite old and it appeared in the literature in 1668. Up to 1984 it seemed that Newton's model was enough to solve the problem. But it was found that this was not the case and a renewed interest in the problem appeared. The aim of this paper is to treat the problem of plan collisions of rigid bodies, to classify the different models found in the literature and to present a new model that is a generalization of most of these models.