I.V.Vovk, L.I.Kosovec, V.T.Matsypura, V.N.Oliynik Modeling of the process of sound propagation in human thorax. Part 2. Analysis of acoustic properties in the normal state |
Acoustic bulletin, Vol. 14 ¹ 3, (2011) |
| A numerical analysis of acoustic properties of normal human thorax is carried out on the base of previously developed physical and mathematical models. A topography of different biological tissues in thorax cross-section is taken into account and the tissues themselves are represented with the acoustic media with dissipation. The efficiency of the trachea as a sound source in the thorax is shown to be extremely low. The amplitude of vibrational velocity on the trachea surface is inversely proportional to frequency. The acoustic transparency of the lungs is found to be rapidly decreasing with frequency. At the same time, the acoustic transparency of interpulmonary zones remains practically unchanged in the overall range of 100 to 1500 Hz. Below the approximately 360 Hz, the lung acoustic transparency is higher than that of interpulmonary zones, while at higher frequencies the opposite situation is observed. It is found that considerable decrease of lung acoustic transparency with frequency is caused by low sound propagation velocity in the parenchyma. Therefore, with growing frequency, the characteristic wave dimension of the lung becomes much greater than unity and the role of related acoustic dissipation considerably increases. At frequency of about 70 Hz, a resonance between the lungs (playing the role of equivalent elasticity) and the ribs-and-muscle and fat layers (playing the role of equivalent mass) is discovered. The increase of lung acoustic transparency in the resonance band is noticed. |
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KEY WORDS: thorax, biological tissues, sound pressure, vibrational velocity, acoustic transparency, resonance |
| TEXT LANGUAGE: Russian |