Hey, I legit created an account here to ask you this question (I saw you are still active on this forum).Picking out the heartbeat *acoustically* will be extremely difficult. Since it sounds like direct contact is allowed, consider other technologies. My Polar heart monitor is low cost and transmits the heartbeat by radio to a compatible receiver. Old tech, very reliable.
I'm also trying to have my heartbeat play on a speaker in real time for a research project and I'm seeing my best option might be the Polar heart monitor. How does it transmit the heartbeat by radio to a compatible receiver / what would be a compatible receiver? Thank you!
Moderator edit: new thread created from here.