How do you enable a microphone input in the android emulator

have you seen this tutorial? see the comment:

You guys are not able to record sound in emulator because the android emulator doesn’t support it yet. This code should only work on the phone.

Update

Now it is possible to record audio by android emulators, just need to enable it:

Extended controls (3 dots in emulator control bar) > Microphone > Virtual microphone uses host audio input

In 2021 there is an option in emulator settings to enable computer host microphone.