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Summary: VOLUME 87, NUMBER 8 P H Y S I C A L R E V I E W L E T T E R S 20 AUGUST 2001
Avalanche Dynamics of Crackle Sound in the Lung
Adriano M. Alencar,1,2 Sergey V. Buldyrev,2 Arnab Majumdar,2 H. Eugene Stanley,2 and Béla Suki1
1
Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215
2
Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215
(Received 16 March 2001; published 1 August 2001)
We analyze a sequence of short transient sound waves, called "crackles," which are associated with
explosive openings of airways during lung inflation. The distribution of time intervals between consecu-
tive crackles Dt shows two regimes of power law behavior. We develop an avalanche model which
fits the data over five decades of Dt. We find that the regime for large Dt is related to the dynamics
of distinct avalanches in a Cayley tree, and the regime for small Dt is determined by the dynamics of
crackle propagation within a single avalanche. We also obtain a mean-field solution of the model which
provides information about lung inflation.
DOI: 10.1103/PhysRevLett.87.088101 PACS numbers: 87.19.j, 43.25.+y
The temporal patterns of natural events have been stud-
ied extensively to identify hidden dynamics in various
processes, including such diverse phenomena as mass ex-
tinction in fossil records [1] and popping bubbles in aque-
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