Holo-Hilbert Spectral Analysis Reveals Novel Envelope Features in Heart Sounds

The fundamental heart sounds (S1 and S2) offer valuable insights into cardiovascular health. While the envelope of heart sounds holds significant information, traditional methods have not fully explored its complex spectral features, particularly its frequency and power components, leaving a gap in our understanding of this potentially valuable information. This study introduces Holo-Hilbert Spectral Analysis (HHSA) as a novel approach to extract and analyze both carrier and envelope features of S1 and S2. We identified a distinct envelope frequency range (4–20 Hz) nested within a broader carrier frequency range (16–128 Hz), revealing previously uncaptured modulations in the heart sound. Additionally, differences in the envelope power within this frequency range were observed between normal and abnormal subjects, providing novel physiological insights through the application of HHSA. These findings showcase the potential of HHSA to enhance cardiac diagnostics by providing a more comprehensive understanding of the complex dynamics embedded within heart sounds.