I made a new discovery today and I don't like it. Maybe this is common knowledge for the tech privacy crowd and I'm just late to the party...
Have you ever used your iPhone camera to take a photo and it said the microphone was used on that drop-down menu? That's because, if you have Live Photos on in your camera settings, it records a .MOV file. I found this out when I was transferring some photos in my camera roll to my computer.
I'll use this photo of the AIDS memorial quilt as an example. I was at an exhibit showing some of the quilt and decided to take photos of a few panels. The Live Photo feature recorded 1.5 seconds before and after the photo was taken. The resulting .MOV file became the "live" version.
I unfortunately can't upload the video file with the recorded audio. I think you can hear the audio on your own if you turn the volume up while a Live Photo is playing.
This feature's an opt-out instead of opt-in. You can temporarily turn off live photos by pressing the top-right circle in the Camera app. It can be permanently deactivated in the Settings app by going to Camera > Preserve Settings > Live Photos and turning on preference saving.