Table 3.

Principal algorithm families of detection of the known markers.

Signal	Characteristics and processing [7]	Analysis
Normal sounds
Lungs	Low-pass filtering (between 100 and 1,000 Hz)	Periodogram (power spectral density - PSD), autoregressive models [38]Error! Reference source not found.
Trachea	Noise with resonances [100, 3,000 Hz]
Adventitious sounds
Wheezes	Sinusoid (range ~ 100 and 1,000 Hz; duration >80ms)	Periodogram (PSD), STFT (short-time Fourier transform), FFT, linear prediction of coefficients [69], genetic algorithms [27], neural networks [27],, wavelet [46]
Rhonchi	Series of sinusoid ( <300 Hz and a duration >100ms)
Crackles	Wave deflection (duration typically <20ms)	Temporal analysis [44], FFT, linear prediction of coefficients [45], fuzzy non stationary filter [41], genetic algorithms [27], neural networks [27], wavelet [27] [46]
Snores		Temporal analysis, periodogram (PSD)[38]
Stridors		Periodogram (PSD), STFT, autoregressive models [27] [44]