A closer look
While you are watching a commercial on television, your phone might be silently listening to high-frequency audio beacons hidden in the broadcast. These ultrasonic cross-device tracking signals are completely inaudible to human ears but perfectly clear to the microphone on your smart devices. Marketers use them to link your TV-watching habits directly to your mobile web browsing, creating a seamless map of your behavior. You can block this invisible chatter by routinely revoking unnecessary microphone permissions for apps that don't absolutely need them.
