Yet again, someone mistakes an anecdote for evidence. And evidence is also not the plural form of anecdote.
I’m sure we have people here who are tech-savvy enough to have actually examined the kinds of data that their phone is sharing.
If you have something like Google Home or Amazon Alexa, then yeah, those would be sending voice data back, and yeah, they could probably use it for advertising. But as far as I know, there is no evidence that phones are “always listening” and “always sending information back” when they’re idle.
Fun, sure, but not an experiment that would actually be meaningful.
The data from your phone’s microphone doesn’t magically appear in Google’s advertising servers. It would have to go through a lot of steps before it gets there, and one of the first steps is in your home (if you’re on WiFi). One can analyze the traffic/data that leaves their phone.
It’s good to be cautious, but worrying about your phone’s microphone is potentially like worrying about your windows while leaving your front door open.