Better Resolution in Clinical Phonocardiography

II. The Use of Compressor Phonocardiograph

Abstract

The compressor circuit for the comprehensive study of the cardiovascular sound was described. This circuit arranges the intensity distribution of the precordial vibratory spectrum by a non-linear amplification using diodes. When used with the conventional high-pass filter (compressor phonocardiography), it has a superiority to pick up the feeble vibrations of both low and high frequency ranges, and thus a single high-pass filter permits the recording of both low and high frequency vibrations comparable to those supplied by several conventional filters. Therefore, the number of filter may be reduced. Tentatively, 50/6 and 400/24 filters are satisfactory to pick up all the features of the cardiovascular sounds when the compressor is used properly. Furthermore, because the large vibration is selectively attenuated, a certain width of the recording paper becomes to be available for more beams. Reduced number of filter, the compressed amplitude of the large vibration and the stable baseline, all permit the polygraphic recording and this is particularly preferable to the functional phonocardiography which requires both low and high frequency phonocardiograms from the various auscultatory areas simultaneously. Several cases were illustrated to explain the above-mentioned statement, and the comments were made on the erroneously introduced misconcept of the phonocardiography.