Ultra sound positioning uses audio signals in the range between 18 and 22 kHz. The high-frequency, digital, acoustic signals are not perceptible to the human ear and are transmitted via standard loudspeakers, for example in smart TVs. These do not have to be physical stand-alone devices, such as iBeacons. The term ultrasonic, uBeacon or audio beacon means only the coded signal.
- independent of GPS/Bluetooth
- Available worldwide
- no additional hardware required
- Problems of data protection law
- restricted range
Similar to a watermark, information about the location, for example, is modulated into the signal. This technology is therefore also called audio watermarking. The receiver of the signals is the microphone of a smartphone, which can also decode the signals and trigger the corresponding location-based services, proximity marketing etc. via the corresponding app on the mobile phone. This works over a distance of up to seven meters, as long as there are no walls in between. For example, customers can be provided with discount codes, sale information, etc.
Just like VLC / IPS, ultrasound can also be used for positioning in this way. One advantage of the technology is that it can also be used by users who have deactivated GPS or Bluetooth on their smartphone. uBeacons are distributed as devices under the brand name SonoBeacon™, for example. A uniform standard for the technology is not yet available.
Security experts at the Technical University of Braunschweig have identified at least 234 apps for the Google operating system Android in a study of a total of 1.3 million apps in 2017, which track users across different devices with ultrasound signals. The apps should then send data back to advertisers via the mobile phone and its user unnoticed. This ultrasonic tracking is mainly used in the USA and Southeast Asia. SilverPush tracking software, which is often used, is classified as malware by anti-virus service providers. Among the 234 apps were the fast food chains McDonald’s and Krispy Kreme and the game “Pinoy Henyo”.