PerspectivesAre you interested in submitting a Perspective Article? Be sure to read The Science Advisory Board's Editorial Guides for Perspective Articles. Click here. The Secret of the Human Voice by S. Ziaran This Perspective discusses The Secret of the Human Voice, a publication by Vojtech Misun, Brno University of Technology, 61669 Brno, Czech Republic. The human voice is generated in the vocal organs that are part of the voice system. Sound is generated by airflow passing through the whole vocal system during exhalation or inhalation. The human voice requires activity of two parts of the speech organs, i.e. of the vocal folds and the vocal tract. The vocal folds generate the 'source voice' further adapted by the articulators in the vocal tract to form the resulting voice. A malfunction or defect in one of these parts of the speech organs causes worse quality of the resulting voice or even makes its generation impossible. The author of the publication has studied the human voice for many years: the way it is created and the possibility of its substitution after the total laryngectomy (following removal of the larynx including the vocal folds). It has to be stated that the problems relating to the human voice generation are very complex and not yet completely solved. Although they have been explored by numerous experts in different institutions all over the world, there are still quite a few blank areas left, inviting further research. This work presents the study of how human speech, and primarily the human voice are created. It outlines the mechanism of creation of the human voice and its individual components, i.e. vowels and consonants. The problems concerning the vocal folds function are discussed in greater detail and two theories of their function are described: "myo-elasto aerodynamic theory" of phonation and "compressed air bubble principle generated based on the subglottal pressure characteristics". An adequately formulated theory of the vocal fold function is of course important for possible construction of the substitute vocal folds after the total laryngectomy. There it is necessary to correctly analyze the vocal fold function in healthy humans, look into and define the principle of their function and based on this analysis formulate the principle and construction of the substitute, i.e. artificial vocal fold. In one chapter of the publication, it describes the principle of the vocal fold function called "myo-elasto aerodynamic theory" of phonation. The glottal flow is the main characteristic of this theory of the source voice generation. The flowing air through the vocal folds is therefore the main condition for the creation of the source voice for the relevant vocal fold. The glottal flow defines the amount of air which passes through the glottis in time during each phonation period and is defined by "normalised volume speed", or by "normalised volume speed derivation". So that this theory makes impossible of the voice intensity change to be generated. Departing from a number of flaws and lack in clarity marking the principles defined by different authors in literature so far, the author of the work defined and further develops a new principle of the vocal folds function provisionally named "compressed air bubble principle generated based on the subglottal pressure characteristics", in short "compressed air bubbles". The subglottal pressure characteristic is his relation to the glottis, i.e. the changing opening between the vocal folds during their vibrations. Based on this principle of the vocal fold function, the main forces acting on the vocal folds during phonation are -- subglottal pressure under the vocal folds and in the whole trachea -- flexible forces of the vocal fold muscles acting against the vocal folds opening -- inertial forces of the vocal folds The driving effect for the vocal folds during their phonation is the compressed air in the subglottal space which is always higher than in the supraglottal space. Although the lungs try to maintain constant subglottal pressure in the trachea, as a result of the vocal fold vibrations and through the changing size of the glottis, air is let out into the supraglottal space due to the fact that the subglottal pressure value changes in relation to the glottis size. This relation is called "subglottal pressure characteristic" and is essential to phonation. Within the total laryngectomy the larynx and epiglottis are removed and the lungs are disconnected from the vocal tract. By that the voice organ, i.e., the generator of the source voice, is removed. That means the successful voice reconstruction after the total laryngectomy requires finding or supplying an alternative source voice with an appropriate power source. There are also some possibilities of voice reconstruction after the total laryngectomy, which are introduced in the publication. ### << Previous Next >> [ View All Perspectives ] |
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