Log-frequency spectrogram for respiratory sound monitoring

Computerized patient monitoring provides valuable information on clinical disorders in medical practice, and it triggers the need to simplify the extent of resources required to describe large set of complex biomedical signals. In this paper, we present a new signal quantification method based on block-wise similarity measurement between the neighboring regions in the optimized log-frequency spectrogram of audio signals. Low dimensional cepstral feature set for signal quantification is then formed from the reconstructed similarity matrix using 2D principal component analysis. The effectiveness of the method is verified with real respiratory sound (RS) signals for the purpose of abnormal RS detection towards RS monitoring. Unlike conventional pathological RS detection methods which extract features from well-segmented inspiratory/expiratory phase segments, the proposed scheme is able to perform fast detection of various types of abnormality for unsegmented signals.