Google Pixels have long had a Now Playing feature that can identify songs playing nearby. As far as I know, it’s all on-device and offline. There are pre-loaded hashes of a bunch of common songs which can then be compared to ambient sounds.
So there could be similar on-device functionality that recognizes spoken trigger words and record them to some file which can then be accessed by apps that serve ads.
This would be different from (and more efficient than) recording large audio files and sending them over the internet.
Copying my other comment
Google Pixels have long had a Now Playing feature that can identify songs playing nearby. As far as I know, it’s all on-device and offline. There are pre-loaded hashes of a bunch of common songs which can then be compared to ambient sounds.
So there could be similar on-device functionality that recognizes spoken trigger words and record them to some file which can then be accessed by apps that serve ads.
This would be different from (and more efficient than) recording large audio files and sending them over the internet.