This paper proposes a novel automatic heart sounds segmentation method for deployment in heart valve defect diagnosis. The method is based on the correlation coefficients matrix, calculated between all the heart cycles for similarity identification. Firstly, fundamental heart sounds (S1 and S2) in the presence of extra gallop sounds such as S3 and/or S4 and murmurs are localized with more accuracy. Secondly, two similarity-based filtering approaches (using time and time-frequency domains, respectively) for correlated heart cycles identification are proposed and evaluated in the context of professional clinical auscultated heart sounds of adult patients. Results show the superiority of the novel time-frequency method proposed here particularly in the presence of extra gallop sounds.

We propose a modified version of the standard homomorphic method to design a minimum-phase inverse filter for non-minimum-phase impulse responses equalization. In the proposed approach some of the dominant poles of the filter transfer function are replaced by new ones before carrying out the inverse DFT. This method is useful when partial magnitude equalization is intended. Results for an impulse response measured in the car interior show that by using the modified version we can control the sound quality more precisely than when using the standard method.

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We propose an alternative approach to the Balanced Model Truncation method (standard method). This approach reduces substantially the order of minimum-phase inverse filters for equalizing room acoustics. This method is based on a property of the filter z transform function, which modifies the corresponding FIR coefficients before the application of the standard technique to the modified FIR coefficients filter version. In the standard technique, the Hankel singular values plot is the chief guide for a user for the selection of a reduced filter order. Results for minimum-phase inverse filter corresponding to partial equalization of measured acoustic impulse response show the superiority of the proposed method over the standard technique, in terms of reduced filters order selection.