[oceanghost]

I believe this is happening, or will be shortly. I've had these weird experiences as well.

But one casual experiment is not proof. I assume the implications for battery life alone would make this impractical.

[ksangeelee]

I searched for microphones with an integrated low power DSP, and the first hit [1], from 2016, described a device for always-listening voice activation using an EEPROM configured DSP that claims to consume 0.4mW at 1.8V (0.22mA). That seems astonishingly low, and would be unnoticeable in terms of battery drain on a modern smartphone.

While the article describes a 'trigger to activate' scenario, I guess the DSP could also be configured to output data at an earlier stage in the chain for post-processing on a server. The volume of data would be orders of magnitude lower than sending raw waveforms. Of course, this would introduce the need for some memory for buffering, which eats into the power budget, but having read about this device, I'm pretty convinced that it's technically feasible.

Whether or not phones actually do this at a low level is another matter. It would be an interesting experiment to graph the current draw from a sleeping phone's battery while conversations were being spoken into the mic.

[1] https://www.sensorsmag.com/components/mic-hears-all-all-time

[jpl56]

I understand that an app recognizes keywords by itself. Then it doesn't need to send any heavy sound data to the server. A simple "send an ad for uni" transaction is sufficient.

I believe any microphone-authorized app (e.g.: Facebook) can do it, preferably when the phone sits on the table. "Buy", "Need", "Wish" are good keywords when they are followed by another word that sells easily : "shirt, phone, watch, ..."