Figure 11From: Digital Subtraction Phonocardiography (DSP) applied to the detection and characterization of heart murmurs Sample PCGs (first & second panels) from a patient with an ASD. The murmurgram (third panel) between S1 and S2 isn't "flat". The murmur has frequency components that extend to around 400 Hz. The second heart sound is clearly split in both PCG waveforms (Clinical Case 4).Back to article page