Digital subtraction phonocardiography offers one the ability to separate the deterministic components of heart sounds (typically S1 and S2) from associated murmurs via digital subtraction. In this patient with a systolic murmur from a VSD (Ventricular Septal Defect) two successive heart sound cycles (PCG1 and PCG2) are subtracted to produce a “murmurgram” whose Color Spectrogram (CSP) is presented in the bottom panel. Image used under a Creative Commons Attribution License 4.0 from Akbari MA, Hassani K, Doyle JD, Navidbakhsh M, Sangargir M, Bajelani K, Ahmadi ZS. Digital Subtraction Phonocardiography (DSP) applied to the detection and characterization of heart murmurs. Biomed Eng Online. 2011 Dec 20;10:109. doi:10.1186/1475-925X-10-109. PubMed PMID: 22185298; PubMed Central PMCID:PMC3258229.