Does laryngeal noise contribute to the vesicular lung sound?

The precise sound sources that contribute to the vesicular lung sound heard on the chest wall have never been accurately determined. Current thinking favors the mainstem, lobar, and segmental airways as the principal sources contributing to the sound. The larynx has occasionally been said to be responsible for some or all of the vesicular sound, but its actual contribution has never been determined in humans. This study was designed around the hypothesis that, were the laryngeal noise to form an audible part of the vesicular sound heard on the chest wall during quiet breathing, the vesicular sound should get louder during voluntarily produced noisy breathing provided that the sounds are compared at approximately equal flow rates and lung volumes. In this study, sounds from the larynx and 4 sites on the chest wall were simultaneously recorded and displayed along with flow volume loops during quiet breathing and voluntarily produced noisy breathing without actual phonation in 3 healthy subjects. Although increases in amplitude of the laryngeal noise of severalfold were observed in both inspiration and expiration, the amplitude of the simultaneously recorded vesicular sound correlated only with flow rates and were completely unaffected by changes in laryngeal sound amplitude. This demonstrates that during quiet breathing in healthy subjects no detectable component of the laryngeal noise reaches the periphery.