There are many apps that can potentially be using the microphone on your device to be listening in to your surroundings. Here's how to opt out of those pesky-nosy-parkers using that information to determine which advertising may be delivered to you!.
Article mentioned in the video above: https://betanews.com/2018/01/02/alphonso-mobile-audio-targeted-ads/
Step by step guide on how to opt out: http://alphonso.tv/mobile-opt-out-guide/