Abstract
As an approach to investigate the manner with which the cardiovascular sounds and murmurs are transmitted, the intensity distribution of the sounds or murmurs on the surface of the chest wall was studied. The way of transmission of waves with the vibration of unitary frequencies to the surface of the chest wall was also studied through the examination of the intensity distribution of each vibration. Material and Methods The first and second heart sounds in 8 young normal men (19 to 25 years old), and the systolic murmurs in 7 patients with small. ventricular septal defect (19 to 33 years old) were studied. The apparatus for this study consisted of a moving coil direct-contact microphone, a pre-amplifier, a band pass filter with self-contained AC amplifier, an attenuator, a cathode-ray ocilloscope and a long-recording camera. In 6 normal men (19 to 24 years old), the way of transmission of the vibrations to the surface of their chest wall was studied. For this purpose, an oscillator, a frequency counter, a voltmeter, a vibrator, a moving coil direct-contact microphone, a band pass filter and a level recorder were used. Results The frequency intensity spectra of the first and second heart sounds at the points of maximum intensity on the chest wall were examined in one of the normal subjects. The same characteristics were investigated in one of the patients with ventricular septal defect at the point of maximum intensity of the murmur. The higher the cycle of their component frequency among the spectra of the normal heart sounds was, the lower the intensities of the first and second heart sounds became, that is, the intensities decreased at a rate of 15 decibels per octave for the frequency range of 50 to 1008 cycle per second. The same relation was observed between the frequency and the intensity in the spectrum of the murmur of V.S.D. (Roger's murur), that is, the intensity decreased at a rate of 6dB/ octave for the frequency range of 50 to 504cps and at a rate of 18dB/octave for 504 to 1008 cps.
