There is a chance your phone has been tossing out ultrasonic tones to be picked up by other devices. Sounds that the human ear cannot pick up but devices can.
The German government hired a research team and they discovered that more than 230 apps on the Androids market hosted by Google, were secretly tracking users through the use of ultrasonic audio. The ultrasonic beacons can help the apps manufactures create intimate profiles on people, and also be able to tie them into your other devices that are communicating with said beacon.
It works like this: Let’s say your at your friends place , and his smart TV uses the beacon, and you are watching your favorite tv show that comes on every week. Let’s also assume that you have the Mcdonalds app on your phone as well. Now, a Mcdonalds commercial comes on the TV. During this commercial an ultrasonic tone is sent out and picked up by your Mcdonalds app on your phone. Now Mcdonalds knows that your watching what ever show at what ever time. They learn more and more information about you. Now let’s say your friend also has this app. His phone also picks up the ultrasonic tone. Now Mcdonalds knows that you and your friend both watch whatever show every week at this certain time.
This just goes to show you that we are not as private as we may think. How many other applications are doing this that haven’t been caught? And to take this a step further, what devices are listening into our conversations with out our knowledge or consent?