Spatial distribution of pulmonary sound transmission

Sonic noise transmission from the mouth to the posterior chest wall was measured in 11 healthy subjects. The ratios of transmitted intensities R to analogous sites over the right (R) and left (L) lung fields were estimated over 3 frequency bands: 100–600, 600–1100, and 1100–1600 Hz. A significant R to L dominance in R was observed at the upper site at low frequencies and conversely, a significant L to R dominance was observed at the lateral site at high frequencies. A theoretical model of sound transmission that includes the asymmetrical anatomy of the mediastinal structures is in agreement with the observations at low frequencies. These findings suggest that the pathways of sound transmission to the chest wall change significantly over the measured frequency range.