I am sorry that happened to you. I was recording a good amount of video that was important to me and my video recording DIDN'T record sound. I had to buy sound recording lapels and other cheap equipment to compensate.
After I bought the microphone, I was able to determine that the sound did work and it was simply not playing at the time.
The iPhone has more AI in it than most laptops. It sets some things automatically, and may have enabled a setting that is causing a problem.
I don't know what the exact setting would be because there is quite a bit missing from your post.
I used to troubleshoot problems on my Windows laptop without having to touch the registry, usually a reboot would work.
Please provide a little more background and under what conditions the white noise/screeching occured.