Non-linear digital filters for extracting crackles from lung sounds.
A non-linear digital filter system is proposed for automatic extraction of crackles which are discontinuous paroxysmal sounds in lung sounds. This system is composed of two filters: one is a stationary-non-stationary separating filter and the other is a width separating filter. The former separates non-stationary signals from stationary ones, using the prediction error for the input. This filter can roughly separate the crackles as non-stationary signals. The latter, the width-separating filter, performs signal extraction on the basis of the interval between the zero-crossing points of the non-stationary signals, simply realized by logical algebra. This filter extracts a small-width impulsive signal and its succeeding waves; such a waveform is typical of crackles. Crackles can be more precisely extracted from the non-stationary signals by this filter. Both of the filters are realized quite simply. The high performance of this system is shown in processing actual lung sound data.
Arakawa
K
K
Department of Computer Science, Meiji University, Kawasaki, Japan.
Harashima
H
H
Ono
M
M
Mori
M
M
D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008433:Mathematics; D011658:Pulmonary Fibrosis / Q000503:physiopathology; D012135:Respiratory Sounds; D012815:Signal Processing, Computer-Assisted