Arakawa K, Harashima H, Ono M, Mori M
Department of Computer Science, Meiji University, Kawasaki, Japan.
Front Med Biol Eng. 1991;3(4):245-57.
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.
提出了一种非线性数字滤波系统，用于自动提取肺音中作为不连续阵发性声音的爆裂音。该系统由两个滤波器组成：一个是平稳-非平稳分离滤波器，另一个是宽度分离滤波器。前者利用输入的预测误差将非平稳信号与平稳信号分离。该滤波器可以大致将爆裂音作为非平稳信号分离出来。后者，即宽度分离滤波器，基于非平稳信号过零点之间的间隔进行信号提取，通过逻辑代数即可简单实现。该滤波器提取窄宽度脉冲信号及其后续波形；这样的波形是爆裂音的典型特征。通过该滤波器可以从非平稳信号中更精确地提取爆裂音。这两个滤波器的实现都非常简单。该系统在处理实际肺音数据时表现出高性能。
