The design of the external microphone consists of an acoustic stethoscope diaphragm, hollow tube, 3.5 mm mini-plug condenser microphone with frequency response 50–18,000 Hz and a 3.5-mm microphone adapter for mobile phones. We fix the diaphragm to one end of hollow tube and microphone to other end of the hollow tube. Fig.3 shows the customization of external microphone.This customized microphone replaces the need for the second mobile which is used to measure heart sounds in Fig. 1.