Use of the fast fourier transform for frequency analysis of the first heart sound in normal man

Abstract

The first heart sound of 29 normal, young males, recorded at the apex of the heart, was analysed for the power content as a function of frequency using the technique of the fast Fourier transform. The frequency spectra were seen to contain peaks in the low-frequency range (10–50 Hz) and the medium-frequency range (50–140 Hz). The average spectrum of the entire study shows a peak at 30 Hz, and an average attenuation of the first heart sound at the apex, of 16 dB/octave. The peaks are probably related to the elastic properties of the heart muscles and the dynamic events causing the first sound. Therefore important diagnostic information might be obtained from frequency studies of heart sounds. Such studies should increase the clinical importance of phonocardiography.

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