After more than two years of research and testing, we have finally worked out a solution that Android microphone sound can be streamed to PC. Here is the detailed guide on how to synchronize the Android audio and video when mirroring.
1. First of all, you need to update ApowerMirror to the latest version both on your Android and PC. Click on here to check if you are using the latest version.
2. Open ApowerMirror and go to Settings from the upper left corner. Enable Cast microphone audio.

3. Then back to the main interface and tap the blue M button. Select your computer name and tap Phone Screen Mirroring. In the prompt, click ALLOW.

4. Then you can cast Android microphone sound to PC successfully.
Note: Please keep the phone and computer a little away from each other to avoid loud noise when mirroring.