Abstract
1) Spectral phonocardiography was studied by the use of Sound-spectrograph. 2) Spectral phonocardiography gives better frequency analysis than the ordinary phonocardiography and the use of amplitude display gives better expression of variation in amplitude. 3) The use of ear-like characteristics for the preamplifier gives better recording than the flat characteristic used by McKusick. 4) Using the characteristics of spectral phonocardiography, frequency distribution of heart sounds and murmurs, especially their variation according to auscultatory area, was studied. Noise similar to heart murmur was experimentally produced and some considerations were made on the origination mechanism of heart murmurs.
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