Systems and methods for quantifying the duration of S1 and/or S2 heart sounds, in order to identify markers of heart failure and/or lung failure, are provided. Cardiac cycles containing S1 and S2 sound can be identified in a phonocardiogram and normalized. In order to quantify S1 and S2 sound length, the envelope of the absolute value of the signal can be obtained for each cycle. The sound waves of two components can be separated using the identified single sound wave. These features can be correlated to measures of heart failure and/or lung failure.