Hi erictheise,
Welcome to Apple Support Communities. We understand that you're having an issue with your microphones on your iPhone 8. We'd like to help.
You mentioned that the article you looked at was not helpful. While it may not have fixed your issue, it may have told you some good information about which microphone isn't working. Let's see if we can isolate that a bit more so we can work on a plan to help you get it resolved.
When you say it works when recording a video, does it record audio when you are using the rear facing camera, the forward facing camera, or both? Since different microphones are used each time, knowing how each works will be helpful. The microphones used here are by the camera on rear facing videos and by the receiver in forward facing videos.
You then mentioned that the microphones weren't working when you were on the phone or using Voice Memos. When on the phone, are you holding the iPhone to your ear? If so, that uses the microphone on the bottom of the phone and you may be having an issue with that one. With Voice Memos, it depends on how you're recording the memo as to which microphone it uses but it would either be the receiver microphone or the bottom microphones.
Using that information, are you able to isolate this issue to a specific microphone? Let us know what you find.
Cheers!
