Physical characteristics of pulmonary artery stenosis murmurs in calves

To better understnad the characteristics of cardiovascular murmurs and turbulent energy transmission, we made simultaneous measurements of pressure (sound) and velocity fluctuations in the vicinity of surgically produced stenoses in the pulmonary artery of calves. We did a spectral analysis of these data and found an identifiable break frequency at which the slopes of the pressure fluctuations changed. By use of these break frequencies and the corresponding blood jet velocity and vessel diameter measurements, Strouhal numbers were calculated. The jet velocity, Reynolds number, Strouhal number, and unsteadiness parameter values changed when the vessel was stenosed. When the power spectrum curves for the velocity fluctuations and the sound were compared, they tended to show a correlation between break frequencies. We speculate that this apparent correlation indicated a transfer from turbulent to acoustic energy.