Fig. 7.

Murmur elimination effect for heart sound containing S4 and systolic murmurs using the three methods. a Is the non-murmur-reduced heart sound, and b–d show the sounds filtered by ALPF, WT and 200-LPF, respectively. In the calculation of $SMR,U=U1+U2+···+U6$, and $V=V1+V2+V3$