V.N.Oliynik Effect of viscosity of the air on the sound propagation in human bronchial tree |
Acoustic bulletin, Vol. 5 ¹ 3, (2002) |
| Within the long-wave approximation the physical model of the sound propagation through a transitional zone of human respiratory tract is developed. At that the basic notice was given to the analysis of influence of a viscous interaction between the bronchial air, that oscillates owing to acoustic excitation, and the wall of the bronchus. To avoid consideration of effects of compliance of the walls and the sound radiation into pulmonary parenchyma, in the given study the respiratory airways were modelled by tubes having rigid walls. It is clarified that account of viscosity of air results in appearance of not only damping, but also profoundly expressed dispersion of sound waves diffusing in elements of a bronchial tree. With decrease of calibre of a bronchus these phenomena become more and more appreciable. Account of viscosity also essentially influences the nature of frequency dependences of an input impedance of terminal bronchioles loaded at a system of respiratory airways. Besides, it is shown that the impedance of terminal bronchiole depends on boundary conditions on an input of a respiratory tract at the part of a voice slot (opened or closed vocal chords). |
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KEY WORDS: bronchial tree, transitional zone, branched waveguide, viscosity, impedance |
| TEXT LANGUAGE: Ukrainian |