Acoustical resonance analysis of airway structure

Differences in the spectrum of reflected sound for mechanical airways models of different structure are examined. Two mechanical lung models were designed and built for this study. The first used a silicon lung model, the Zavala lung. The second model consisted of a rigid plastic Y-piece connection with the stem forming the trachea and the two branches, the major bronchi. Comparison of spectra for 100-4000 Hz for the two models showed similarities in the locations of the resonant peaks between 300 and 2000 Hz. The spectra for frequencies above 2500 Hz were very different. The Zavala model spectra display multiple peaks between 2500 and 4000 Hz. In contrast, the simple model showed no significant power above 2500 Hz. This result indicates that spectra analysis of the reflected sound can be used to identify the presence of the smaller airways in the Zavala model