Abstract
Using the technique of the fast Fourier transform, the influence of the circuit fluid and the closing pressure to the closing sound of SJM valve was studied by the power-spectrum analysis. Using the water as the test fluid, the power-spectrum curve of the closing sound showed two peaks at the points of 0.8 and 2.5 KHz, but using glycerol, the curve indicated one large peak at 0.7 KHz and a smaller peak at 2.1 KHz, and the power declined over 3 KHz. The power-spectrum curve showed no changes with the closing pressure change from 50 to 1.50 mmHg. By the fibrin glue attachment to the SJM valve ring, the power of each peak declined both in water and in glycerol. This change can be considered to suggest the thrombus formation of the SJM valve in the clinical state. The power-spectrum curve of closing sound of the SJM valve was changed by the circuit fluid, but not changed by the closing pressure.
