title: The optimal method for recording prosthetic heart valve sounds in clinical situations.
abstract: BACKGROUND
  Valve sounds are thought to be useful in evaluating the functioning of prosthetic heart valves. In previous reports, two recording instruments have mainly been used, a condenser microphone (instrument A) and an accelerometer (instrument B), respectively. This study aimed to investigate the applicability of these conventional devices in recording mechanical heart valve sounds in daily clinical situations. In addition, two other instruments, namely, a stethoscope including a small microphone in its tube (instrument C) and an electrostethoscope (instrument D), were proposed and examined.
  
  
  METHODS
  Mechanical valve sounds were recorded from postoperative patients using each-device and the signal to noise ratio (SNR) of each was calculated. Frequency characteristics of the two newly proposed instruments were also investigated by recording a sweep signal in an anechoic chamber.
  
  
  RESULTS
  The SNR values of the new instruments were significantly superior to those of conventional ones (A, sound signals were not defined from noises; B, 0.97 +/- 0.59 dB; C, 11.5 +/- 4.7 dB; and D, 9.4 +/- 3.5 dB, respectively p<0.05). The frequency characteristics of the two newly proposed instruments were also shown to be acceptable (under 10 kHz), though resonance frequency peaks were observed.
  
  
  CONCLUSIONS
  Two newly proposed instruments can record mechanical heart valve sounds more noiselessly and with more ease than previous ones, and their frequency characteristics are acceptable.
authors.affiliation: Department of Cardiovascular Surgery, Osaka City University, Graduate School of Medicine, 1-4-3, Asahimachi, Abeno-ku, Osaka 545-8585, Japan. ybito@med.osaka-cu.ac.jp
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Bito
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Soeta
authors.forename: Seiji
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Shibata
authors.forename: Shigefumi
authors.initials: S
authors.lastname: Suehiro
mesh_terms: D000162:Acoustics; D000368:Aged; D000669:Amplifiers, Electronic; D004867:Equipment Design; D005260:Female; D006347:Heart Sounds; D006350:Heart Valve Prosthesis; D006351:Heart Valves / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D019023:Stethoscopes