To use an electret condenser mic, you need power, a resistance to bias the FET inside the mic, and a capacitor to remove the DC.

In the video, I show the output voltage of the capsule mic using a cheap oscilloscope.

This is the datasheet for the electret condenser (capsule) microphone I uses in the video:
https://www.cuidevices.com/product/re...

See my comment below about proper value for RL, the load resistor.