The mechanism of transmission of the cardiovascular sound. An experimental study of the conduction velocity of sound on the chest wall.

Abstract

The conduction velocity of sound during the transmission over the chest wall was investigated. In the present experiments, a vibrator, which was connected to an audiooscillator producing a sinusoidal signal of a single frequency, was applied to a place on the chest wall as an external source of sound. The conduction velocity was calculated from the time delays in arrival of the vibration at several places on the line drawn from the site of the external source.The conduction velocities of the vibration on the chest surface were from 5.9 to 12.3M. per sec. for 50cps, 11.5 to 15.7 for 100cps, 16.7 to 40.9 for 200cps and 18.2 to 39.0 for 400cps, respectively. The velocities were found to increase proportionally with the square root of the frequency.From these data, it was clarified that 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, it was suggested that 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.