Classification of heart valve sounds from experiments in an anechoic water tank

Technical Report · Tue Jun 01 04:00:00 EDT 1999

DOI:https://doi.org/10.2172/10788· OSTI ID:10788

Axelrod, M C ^[1]; Clark, G A; Scott, D

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1. LLNL

In vivo studies in both sheep and humans were plagued by a number of problems including movement artifacts, biological noise, low signal-to-noise ratio (SNR), chest-wall reverberation, and limited bandwidth recordings as discussed by [1]. To overcome these problems it was decided to record heart valve sounds under controlled conditions deep in an anechoic water tank, free from reverberation noise, including surface reflections. Experiments were conducted in a deep water tank at the Transdec facility in San Diego, which satisfies these requirements. The Transdec measurements are free of reverberations, but not totally free of acoustic and electrical noise. We used a high quality hydrophone together with a wide-band data acquisition system [2]. We recorded sounds from 100 repetitions of the opening-closing cycles on each of 50 different heart valves, including 21 SLS valves and 29 intact valves. The power spectrum of the opening and closing phases of each cycle were calculated and outlier spectra removed as described by Candy [2]. In this report, we discuss the results of our classification of the heart valve sound measurements. The goal of this classification task was to apply the fundamental classification algorithms developed for the clinical data in 1994 and 1996 to the measurements from the anechoic water tank. From the beginning of this project, LLNL's responsibility has been to process and classify the heart valve opening sounds. For this experiment, however, we processed both the opening sounds and closing sounds for comparison purposes. The results of this experiment show that the classifier did not perform well. We believe this is because of low signal-to-noise ratio and excessive variability in signal power from beat-to-beat for a given valve.

• Research Organization: Lawrence Livermore National Lab., CA (US)
• Sponsoring Organization: USDOE Office of Defense Programs (DP) (US)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 10788
• Report Number(s): UCRL-ID-134634--Rev-1; AC1005000; AC1005000
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
ACOUSTICS
ALGORITHMS
DATA ACQUISITION SYSTEMS
HEART
IN VIVO
SHEEP
SIGNAL-TO-NOISE RATIO
SPECTRA
TANKS
VALVES
WATER