sthetoscope digital - electret condenser mic (ecm)

[ramdani_febrian]

i make sthetoscope digital using ecm,
can't capture heart sound but can capture sound outside the sthetoscope.

note : if i using stetoscope without ecm,
ecm is replace with my ear, i can hear the heart sound,

what is wrong with my stetoscope??

[NottheDan]

Are you using a sound chamber or are you trying to pick up the sound directly?

[Audioguru]

I corrected an analog electronic stethoscope project. As a sound chamber (stethoscope head) for its electret microphone I used a plastic lid from a jar of peanut butter:
"Fasten the microphone to the stethoscope head with a rubber isolating sleeve or use a short piece of rubber tubing on its nipple. A thick jar lid can be used as a stethoscope head. The microphone must be spaced away from the skin but the stethoscope head must be pressed to the skin, sealing the microphone from background noises and avoiding acoustical feedback with your headphones.

The microphone/stethoscope head must not be moved while listening to heartbeats to avoid friction noises.

Protect your hearing. Keep the microphone away from your headphones to avoid acoustical feedback."