The sound from the video and your voice share the same microphone on your device. So if you can only hear the video and not your voice, it is possible that your volume is turned up too loud. Try turning the volume down a little and record again.
For iPhone 7 and above, please follow these instructions:
- Go to device settings > General > Accessibility
- Under the "Hearing" setting, adjust the audio balance all the way to the left. This will make the sound from your video come out from just the bottom speaker.
- Try recording your video again!
Tip: Try recording in a quiet place so that you do not need to turn your phone volume up too much so your video will turn out on point!