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In the never-ending quest to track audiences, advertising companies have developed an even creepier technology to monitor your behavior. High-frequency sounds that are inaudible to users — also called audio beacons — are broadcast from TVs and browsers, and then give advertisers the power to track nearby smartphones, tablets, computers and various other electronic devices under a single identity.

These cross-device tracking audio beacons are being developed by companies like SilverPush, according to a filing by the Center for Democracy and Technology (CDT), a Washington D.C.-based non-profit organization. The audio beacons only work, though, if the smartphones and other devices in a household have apps installed that contain SilverPush’s — or one of their competitor's — technology.

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The CDT reports that apps containing SilverPush's software can report “which ads the user saw, how long the user watched the ad before changing the channel, which kind of smart devices the individual uses, along with other information that adds to the profile of each user that is linked across devices.”

This process is seen as more valuable to advertisers than the cookie files that track user activities. The CDT says that the audio beacons create "supercookies," which are locally stored files that can’t be removed as easily as users can clear cookies.

According to the CDT, Adobe is also considering getting into this market with a cross-device identification system, which would "deterministically track users across devices in the form of a data-sharing cooperative among users." Adobe would be sharing this data, supposedly in a hashed, anonymized form, with partners, in a way that would "better connect the dots between its consumers/prospects and their devices."

In anticipation of a Federal Trade Commission workshop today (Nov. 16), the CDT has expressed that “increased transparency and a robust and meaningful opt-out system” are required for responsible use of this technology.