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. 2019 Aug;16(8):967–969. doi: 10.1513/AnnalsATS.201901-022IP

Figure 2.

Figure 2.

Liquid plug propagation and rupture causing crackle sounds. The plug travels at speed V in a tube of radius a, because of the air pressure difference P1 − P2. Inspiration starts at time t1; the plug thins at t2 and ruptures at t3 to t5, reopening the airway. The surface tension is σ.