GLOSSARY OF TERMS USED IN TIME SERIES ANALYSIS
OF CARDIOVASCULAR DATA
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SPECTROGRAM

Method for the study of nonstationary signals based on splitting the signal in short-time sliding windows and on getting the Fourier spectrum in each window, in order to obtain a time-varying spectral description.

The spectrogram is computed as the modulus squared of the short-time Fourier transform, i.e. a windowed Fourier transform. The window length should be short enough that the signal may be considered more or less stationary, and that events may be located in time with sufficient resolution. On the other hand, it should be sufficiently long to guarantee an appropriate frequency resolution.

Spectrogram of systolic blood pressure obtained from an invasive 24-h blood pressure monitoring by sequentially splitting the signal in 4-min long,  overlapped data windows, and by computing the FFT spectrum in each window (the start of the recording was at 6pm).

M. Di Rienzo et al (1989) 24-Hour Sequential Spectral Analysis of Arterial Blood Pressure and Pulse Interval in Free-moving Subjects IEEE Trans. BME

(PC 25-02-2000)

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