Crackle pitch (spectral frequency) calculated from 4 half-periods: , , , and , Figure 1(a)
Ratio of the 2nd and 1st half periods
Half-period duration variability (%)
(Standard deviation %)/(mean )
Crackle timing (timing)
Crackle timing is defined as follows: 1 for early inspiration, 2 for mid-inspiration, 3 for late inspiration, 4 for early expiration, 5 for mid-expiration, 6 for late expiration
Crackle transmission coefficient (CTC)
The degree of crackling sound transmission through the ipsilateral chest, as calculated from crackle family observation by multiple microphones. The CTC has a value of 0% in the absence of any transmission and 100% when there is equal transmission to all ipsilateral channels see [7] for detailed description and discussion.