Ultrasonic cross-device tracking. Audio "beacons" can be embedded into television advertisements, like radio beacons. When picked up by smartphones, allow behavior of users to be tracked - Upgoat

Ultrasonic cross-device tracking. Audio "beacons" can be embedded into television advertisements, like radio beacons. When picked up by smartphones, allow behavior of users to be tracked
submitted by Conspirologist to Interesting 15 hoursJun 18, 2025 03:55:43 ago (+2/-1) (en.wikipedia.org)
https://en.wikipedia.org/wiki/Cross-device_tracking

This is why phones with the Facebook app installed have shorter battery life. That shit is constantly listening for those tones.