  Collapsible tubes can be employed to study the sound generation mechanism in
the human respiratory system. The goals of this work are (a) to determine the
airflow characteristics connected to three different collapse states of a
physiological tube and (b) to find a relation between the sound power radiated
by the tube and its collapse state. The methodology is based on the
implementation of computational fluid dynamics simulation on experimentally
validated geometries. The flow is characterized by a radical change of behavior
before and after the contact of the lumen. The maximum of the sound power
radiated corresponds to the post-buckling configuration. The idea of an
acoustic tube law is proposed. The presented results are relevant to the study
of self-excited oscillations and wheezing sounds in the lungs.
