Facebook isn't discretely using your phone's microphone to pick up information that could assist with ad targeting, says the social network. This claim has been tossed around for years, though it's stemmed more from a general concern than any strong evidence of eavesdropping.
In response to a tweet about the topic, Facebook's VP of ads, Rob Goldman, denied the company has ever used that tactic to gather information.
I run ads product at Facebook. We don't - and have never - used your microphone for ads. Just not true.— Rob Goldman (@robjective) October 26, 2017
Most of the "evidence" supporting this idea comes from people reporting the appearance of ads for items they've only discussed aloud and haven't typed in anywhere. Given there hasn't been hard evidence of Facebook's app recording data from a phone's microphone, that evidence is pretty weak and has other explanations.