Sound envelope averaging and the differential diagnosis of systolic murmurs.

Phonocardiography previously has been limited in scope because the attained suboptimal signal-to-noise ratio has interfered with the sensitivity and clarity of recordings. A new system is described that reduces this problem by utilizing demodulation and synchronous averaging of the "envelop" of cardiac sounds. A limited survey of the differential diagnostic capabilities of this technique is presented for 80 patients having one of six common forms of pathological systolic murmurs and an 89 per cent diagnostic accuracy is demonstrated. This system promises to be a valuable noninvasive adjunct in cardiologic diagnosis research and education.