This is a imitative heartbeat recording. I recorded using a contact microphone (Korg CM-200) connected to my Focusrite 2i2 interface. I attached the microphone to the tip on my middle finger, then with my middle and index finger tapped gently where my finger meets my palm.
This recording features a steady heartbeats the becomes progressively slower and softer, until finally it stops.
I used a Low pass filter to remove most of the treble making the recording sound more accurate to an actual heartbeat. I also removed a low buzz caused by be having to crank the gain high to get my intended sound.