Power spectra accuracy improvement by optimal signal epoch selection: an heuristic approach

The problem of epoch selection in frequency analysis of biomedical signals often involves tradeoffs between the physiological system studied stationarity, the spectral resolution required, the need for dynamic investigations implying shorter epochs, etc. The accuracy of the spectra strongly depends on the epoch length. We propose a method for optimal epoch selection introducing the notion of 'quality of power spectra'. Two criteria for quantitative estimation of spectral quality are defined, considering a quality to be high when more power is concentrated in narrow frequency bands. A synthesized signal is used for describing the procedure developed and evaluating the accuracy. Noise sensitivity is assessed by adding intensive noise to the signal. Hundreds of synthesized signals are used for validation of the method and some initial experiments with heart rate variation data are presented.