Inaudible audio tracking is IMO almost always against users informed consent, so apps doing it should be suspected as malware.
Roughly speaking, by applying its own random signal modulated the same way the hidden tracking signal is modulated.
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if you don't know the encoding, you'll afaik need way more noise than the tracking signal itself, right?
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since otherwise the encoding can average out the noise while adding up the signal?
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and the ad creator has the advantage of being able to modify individual components of the signal
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and the TV needs to operate in realtime, the attacker doesn't
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and for ads, if nothing else works, you can manually create 2 variants each in N places and get 2^N combinations
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(with the disadvantage that you then have to ship information about individual ads to phones)
End of conversation
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