The Mechanism of Transmission of the Cardiovascular Sound

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Abstract
The conduction velocity of sound during its transmission over the chest wall was investigated. A vibrator, which was connected to an audiooscillator producing a sinusoidal signal of a single frequency, was applied on the chest wall as an external source of sound. The conduction velocity was calculated from the time delay in the arrival of vibration at several places on a line drawn from the site of the external source. The conduction velocities of the vibration on the chest surface were from 5.9 - 12.3 M/sec. for 50 cps, 11.5 - 15.7 for 100 cps, 16.7 - 40.9 for 200 cps and 18.2 - 39.0 for 400 cps, respectively. The velocities were found to increase proportionally with the square root of the frequency. A part of the energy of the vibration spread in the chest wall in the form of transverse shear wave or surface wave, but not in the form of longitudinal compressional wave (sound wave). Accordingly, the vibrations arising from the cardiovascular system might be transmitted in the surrounding structures of their sources in the form of transverse shear wave or surface wave.