The major objective of the proposed work is to determine if inspiratory breath sounds originate in the trachea. The overall hypothesis to be tested is: Turbulent velocity fluctuations, which arise from inspiratory flow through the larynx, produce pressure fluctuations on the tracheal wall, which, in turn, are detected externally to the chest as sound. Both cast model and in-vivo experiments will be performed to evaluate this hypothesis. Preliminary studies have been performed to develop a method for using hot film anemometry to measure velocities in the large airways in-vivo. Initially, a cast model of the larynx and airways down to the sixth generation will be built. Flow visualization experiments in the cast will determine the general nature of inspiratory flow in the large airways. Based on these first experiments, velocities and wall pressures in the cast during inspiration will be recorded and correlated. These correlations will be served as a guide to the in-vivo measurements, which will correlate measured velocity fluctuations and inspiratory breath sounds. This correlation will be used to determine whether inspiratory sounds originate with the turbulence in the trachea. Completion of these studies will increase understanding of the origin of inspiratory breath sounds and specifically determine if the trachea is the site of sound production.
