Noise and disturbance reduction for heart sounds in cycle-frequency domain based on nonlinear time scaling
Hong Tang1, Ting Li, Tianshuang Qiu
1Department of Biomedical Engineering, Dalian University of Technology, Dalian 116024, China. tanghong@dlut.edu.cn
Abstract:
Through an investigation of various clinical cases, heart sounds are found to be quasi-cyclostationary. Nonlinear time scaling from cycle-to-cycle is proposed to enhance cyclic stationarity, where nonlinear time scaling is approximated by a piecewise linear function. The techniques of cyclostationary signal processing are employed in this paper to reduce noise and disturbance in the cycle-frequency domain. Heart sounds can be theoretically recovered in the presence of additive, zero mean noise, and disturbance (perhaps non-Gaussian, nonstationary, or colored). The experimental tests in various conditions confirm the theoretical results.
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