Facebook is working on controversial software which lets it secretly order users’ smartphones to start recording audio whenever they hear inaudible messages hidden in television adverts.

The social network has always denied rumours that it listens into people’s private conversations and analyses what they talk about so it can show advertising that interests them.

But in a patent application published on June 14 this year, Big Zucker’s research division revealed a system which lets it quietly tell people’s mobile phones to capture ‘ambient audio’.

It allows Facebook to conceal ‘a non-human hearable digital sound’ in the audio of a TV ad or other content.




Although people won’t be able to hear this sound, it contains a ‘machine recognizable’ set of Morse code-style sounds which let it tap out a message to your smartphone and order it to begin recording.

The secret sound could be a very high-pitched voice, Facebook wrote, pitched just above the limit of human hearing.

Mark Zuckerberg’s social network has designed a tool which really will let it monitor people in their own homes (Credit: MEGA, Getty)

When it hears this signal, a phone will then start capturing ambient audio, which Facebook describes as the ‘distinct and subtle sounds of a particular location created by the environment of the location, such as machinery noise, the sound of distant human movement and speech, creaks from thermal contraction, and air conditioning and plumbing noises in a household’.

Now, you might think this sounds like an Orwellian nightmare technology which will let Big Zucker intrude upon our lives in unprecedentedly terrifying ways.

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But Facebook designed it with a specific purpose in mind.

The tech is built to monitor what people watch on their ‘broadcasting device’ so that the adverts they are shown on Facebook are likely to appeal to them.

This would also allow companies to get an accurate sense of the size of the audience which has viewed their promotion.

This illustration shows how televisions will secretly send messages to software in people’s smartphones (Image: Facebook)

Big Zucker testifies hearing on transparency and use of consumer data on Capitol Hil in Washington, DC on April 11, 2018 (Photo: UPI / Barcroft Images)

Here's how Facebook's secret ambient audio recording tech works: Smartphones listen out for signals hidden in adverts or other content which are too high-pitched for humans to hear.

Once they hear this signal, the phone begins recording ‘ambient audio’ including the sound of the advert which contains the code.

This is then analysed to generate an ‘ambient audio footprint’ which is stored on an ‘online system’ along with identify information about the person who owns the phone.

The data is then used to work out whether someone watched an ad or engaged with content. This info is stored to make sure Facebook shows it users adverts they are likely to engage with.

This illustration shows a sound wave hiding an inaudible high-pitched message which can be seen on the left (Image: Facebook)

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By recording the secret message in hidden in the television ad, it allowers advertisers to know whether people sat through their creations – or walked away and did something else.

If a recording of the hidden code is muffled or distant, it would indicate users are far away from the telly. Whilst a loud, clear signal would suggest they were firmly couch-bound and tuned in.

This data about what sort of ads people like is then stored so Facebook can show them content in future that’s perfectly honed to grab their attention.

That’s what Facebook says in its patent, anyway. There is no mention of spying on our private life, invading our privacy, recording our intimate conversations and forcing advertising into the heart of our homes whatsoever.

The patent application is called ‘broadcast content view analysis based on ambient audio recording’.

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