Your smartphone's microphone is a handy tool for advertisers such as this. 
https://news.itsfoss.com/ad-company-listening-to-microphone/
It's FOSS News · This Company Says It Uses Your Phone's Mic to Serve Ads for Facebook, Google, and MoreCreepy behavior confirmed.
this has been going on for years. i love how people kept noticing it, then other people kept gaslighting them.