I just came cross this... Using the iPhone 7 to do some 4K recording. I am recording in my office and there is not external noise very quite office. I noticed on play back that I get occasional static noise very similar to when I turn to a "snow globe TV station" the noise comes and goes and I don't hear any hissing at all from my phone. On the other hand if I record the same video, with the same setting and having the lighting earbuds plugged in the static noise if gone... What's going on?!