I don't see definitive proof one way or the other, but I've never given Facebook microphone access on my iPhone. And many others users claiming they've received

I don't see definitive proof one way or the other, but I've never given Facebook microphone access on my iPhone. And many others users claiming they've received targeted ads haven't either. But something interesting that is being pointed out on Reddit is that they can use your gyroscope to detect vibration and convert it to soundwaves when your phone is on a flat surface. The PM at Facebook denies listening to the microphone, but what about the gyroscope data? Technically, what he is saying could be a true statement, but still invading privacy just as much.