A New Standardized and Calibrated Phonocardiographic System

A phonocardiographic system has been designed and built using standard units of known frequency characteristics. The system is calibrated, as the relative and absolute intensity of the signal can be computed from the records´ amplitude, given the conversion factor of the transducer and the degree of amplification in decibels. The system is standardized. It allows the spectrum to be scanned in bands of 1 octave of 3-db attenuation (therefore ideally flat) with the low-cut-off frequency coinciding with the nominal frequency. A 36 db per octave attenuation for the high-pass section is suggested for the selective recording of the high-frequency vibration of low intensity. Representative phonocardiographic tracings are presented.