title: Heart sound segmentation based on homomorphic filtering.
abstract: BACKGROUND
  Phonocardiography, the digital recording of heart sounds, is becoming increasingly popular as a primary detection system for diagnosing heart disorders and is relatively inexpensive. The electrocardiogram (ECG) is often used when recording the phonocardiogram in order to help identify the systolic and diastolic components. In this study, a heart sound segmentation algorithm has been developed which automatically separates the heart sound signal into these component parts.
  
  
  METHODS
  100 patients with normal and abnormal heart sounds were studied. The algorithm uses homomorphic filtering to produce time-domain intensity envelopes of the heart sounds and separates the sounds into four overlapping parts: the first heart sound, the systolic period, the second heart sound and the diastolic period.
  
  
  RESULTS
  The performance of the algorithm was evaluated using 14,000 cardiac periods from 100 digital phonocardiographic recordings, including normal and abnormal heart sounds. In tests, the algorithm was over 93 percent correct in detecting the first and second heart sounds.
  
  
  CONCLUSIONS
  The automatic segmentation algorithm presented uses wavelet decomposition and reconstruction to select a suitable frequency band for envelope calculations and has been found to be effective in segmenting phonocardiogram signals into four component parts without using an ECG reference.
authors.affiliation: Department of Biomechanics, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran k.hasani@srbiau.ac.ir.
authors.forename: K
authors.initials: K
authors.lastname: Hassani
authors.affiliation: Department of Biomedical engineering, Amirkabir University, Tehran, Iran.
authors.forename: K
authors.initials: K
authors.lastname: Bajelani
authors.affiliation: Department of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Navidbakhsh
authors.affiliation: Department of General Anesthesiology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Dj
authors.initials: D
authors.lastname: Doyle
authors.affiliation: Department of Biomechanics, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: F
authors.initials: F
authors.lastname: Taherian
keywords: auscultation; diastolic period; first heart sound; homomorphic filtering; murmurs; normalized average Shannon energy; phonocardiography; second heart sound; segmentation; systolic period