Google Cross-Device Tracking and Audio Watermarking

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Historical recording Aboriginal Corroboree, Australian Broadcasting Corporation, Some rights reserved

Is Google Using Cross-Device Tracking and Ultra-High Frequency Audio Watermarking?

Advertising on the Web is going through some changes because of how smartphones and tablets track visitors on a site and how advertisements may broadcast high-frequency sounds that may act as audio watermarking that other devices can pick up upon.

Imagine watching TV, and your TV broadcasts a high-frequency sound from an advertisement that your phone hears and shares with the advertiser, who may then track whether you search for or purchase the product offered on a website?

Cross-Device Tracking and Audio Watermarking are well described in the following Irish Examiner article, Future of Mobile: Advertisers and the quest for your data.

If you read that and have some familiarity with how Google works, you may ask yourself if Google has followed such practices like Cross-Device Tracking or has shown any sign of doing so.

In November, the Federal Trade Commission (FTC) held a workshop on Cross Device Tracking, where they investigated practices that different companies were getting involved with, and they did some diving into the topic in a very informative way.

A couple of videos linked to that page are worth watching if you want to become better informed on how Cross-Device Tracking works.

I noticed a couple of recent patent filings at Google that were relevant to the workshop and to that article that fit into these changes and is worth thinking about:

Cross Device Notification

The first of these considers some of the different types of devices that are quickly growing in usage across the Web, such as smartphones and tablets, that don’t use browsers that save cookie files and aren’t tracked type of approach as these Web users travel across the Web.

Instead, these devices often use an Advertising ID, or other means of tracking behavior from one device and sharing that tracking with other devices.

Cross Device Notifications
Pub. No.: WO/2015/200051
Publication Date: 30.12.2015
International Filing Date: 16.06.2015
Inventors: Michael Koss Campbell, Justin Dewitt, Katie Jane Misserly, Dmitry Titov

Techniques for cross-device notifications are provided. An example method includes receiving a first indication of an event detected at a first device associated with a user account, determining one or more characteristics of the event based on the first indication of the event, detecting whether the determined characteristics match at least one selection criterion, automatically identifying a second device from one or more devices associated with the user account, and providing, if the determined characteristics match the at least one selection criterion, the first indication of the event to the second device associated with the user account, where the provided the first indication of the event is displayed at the second device to allow management of the event at the first device from the second device.

Audio Watermarking

This second approach, involving high-frequency audio watermarking using sounds that you wouldn’t even hear, surprised me. The patent itself doesn’t talk about that tracking itself. But, it does share information about what you’ve been subjected to (a particular advertisement) so that your future activities involving that advertisement might then be tracked.

Communicating Information Between Devices using Ultra High Frequency Audio
Pub. No.: WO/2015/195808
Publication Date: 23.12.2015
International Filing Date: 17.06.2015
Inventors: Shyam Narayan, Naveen Aerrabotu, Sreenivasulu Rayanki, Yun-Ming Wang


A client device encodes data into an audio signal and communicates the audio data to an additional client device, which decodes the data from the audio signal. The data is partitioned into characters, which are subsequently partitioned into a plurality of sub-characters. Each sub-character is encoded into a frequency, and multiple frequencies that encode sub-characters are combined by the client device to generate an audio signal. Frequency encoding sub-characters may be above 16 kilohertz, so the sub-characters are transmitted using frequencies inaudible to humans. The audio signal is communicated to an additional client device, which decodes frequencies from the audio signal to sub-characters, combined into characters by the additional client device to generate the data.

The future of advertising and Cross-Device Tracking advertisements on the Web will involve multiple types of devices. It may also involve high-pitched frequency audio watermarking sounds outside of the normal hearing range by human beings. Google now has patent filings that describe its possible use of this kind of technology.

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36 thoughts on “Google Cross-Device Tracking and Audio Watermarking”

  1. I’m not sure how useful the audio watermark feature will be in future – particularly if the tones are only associated with adverts. All that would prove is that your *phone* was subjected to the advertisement.

    I suppose this means we can expect to see audio product placement from programme sponsors in future…

  2. Hi Ben,

    It would tell the device that recorded the watermark when you may have heard the advertisement, enabling it to track your activities after you listened to the advertisement.So, it would be tracking your activities along with the fact that the phone noticed the audio watermark. Other audio watermarks could be associated with particular movies or television shows or songs, so they could track whether or not you purchased merchandise that might be associated with that media. I’ve written about Google tracking a media consumption history as described in Google patents, and Google could collect watermark information about different media that you’ve experienced ( to keep a record of that information.

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  5. Hi Bill,

    This does not surprise me at all. Google has to be seen as being at the forefront of search engine technology or Bing or one of the others would suddenly creep up to take a bigger share.

    Using audio technology is very feasible and I can see how it would work. This does goes to show that in this game, if you don’t keep up to date (on a near daily basis) with the latest Google technology and patents, you will soon be left behind.

  6. Hi Mark,

    There are enough other companies involved in crosff device tracking and audio watermarking that it would be surprising if Google didn’t also get involved. You’re right about paying attention to changes in the industry, because they happen so quickly.

  7. It seems the new age of advertisements are arriving when gadgets will convey high frequency messages.

  8. Those messages aren’t for you though, Justin. They are to alert your phone that you’ve been subjected to a particular ad, so that your actions can be further tracked. I just noticed an interesting and thoughtful article on this topic:

    (no longer available)

  9. Hi
    I would like to post a similar experiences in form of article which strike my mind while going through yours. Thank you for helping me think in that direction as well.

  10. Helpful article, informative .
    How rapidly google changes this type of algorithm ? when it was last changed ?

  11. Hi Niaj

    This was the first time I had seen patents from Google on the topics of cross device tracking and audio watermarking. So, there aren’t a lot of indications that Google has done much with this type of algorithm in the past, nor do they have much of a record in changing what they have been doing for these things.

  12. Thanks for sharing, great read!

    When can we expect another change of the algorithm do you think?

  13. Hi Jakob,

    Thank you. Google has been telling us for the last couple of years that they have been performing tens of thousands of experiments each year, and they’ve admitted publicly to at least 500 changes to Google’s core ranking algorithms (what ever they might actually mean by that phrase) each year. So I expect there to be a change to Google’s algorithm every week, on the average.

  14. “Imagine watching TV, and your TV broadcasts a high-frequency sound from an advertisement that your phone hears, and shares with the advertiser, who may then track whether you search for or purchase the product offered on a web site?”

    Damn, targeted advertising is about to get weird, lol. Not necessarily bad, though – personally I’m always impressed whenever I see an ad from an advertiser who somehow managed to target me really accurately (that is, I have at least an iota of genuine interest in whatever they’re selling).

  15. Hi Bill,
    I don’t fully understand how that will work, and potentially you do not either, but it is worth asking: How do these devices communicate with another? Is it the software or the hardware that is doing the communicating? Perhaps I missed the answer to this because I was partially lost, the idea is so far beyond anything I could have imagined. Thanks so much for the post, very interesting info.

  16. Hi Richard,

    If you log into a website using your web browser on your desktop computer, and then if you log into the website on a mobile device, you’ve let the site know that you are the same person on both devices. It’s possible that both devices might learn of your identity from the collection of data by a lot of websites. Check out this article for a look at how that may be done:

  17. Hi Bill,

    I fell over this article by accident and was…. let´s say a little bit scared about what that could mean for our society. Mmmmhh… everybody would be even more transparent than now. The imagination is somehow creepy, I guess.

    Of course, I understand it will come with benefits in everyday life. But thinking about, that my TV will “talk” to my laptop in high-frequency sounds. Or my tablet to my smartphone and so on.

    I am not surprised Google is a driving this topic. 😉

    Thanks for the article, otherwise I would never have heard of it!

  18. Hi, Bill

    Audio watermarking technology is new for me. Thanks for this amazing information.

  19. Hi Bill
    By following tricks you write in your site I designed Digital Marketing Course in my institute .Thank you very much for your contribution.

  20. Bill,

    Very informative article. It doesnt surprise me at all that Google is involved in this space. It’s a natural progression of their current tracking practices.

  21. Hi Richard,

    It may not be a surprise that Google will possibly be following these processes; but they really haven’t talked about them in much detail in places like any of the Google Blogs.

  22. Interesting article.. this application clearly illustrates that future is driven by IoT like late 90’s is ruled by web etc. but I really couldn’t predict how many years it would take for this technology to be used widely by many companies considering most of the companies still couldn’t even master analytics space

  23. Hi Kiran,

    The FTC did have a workshop on cross device tracking in November, so it’s possible that they could provide some guidelines that may help define how such technology should be used in the future. It is possible that technologies of this type may end up becoming very popular as mobile devices remain popular ways that more and more people get connected to the Web through.

  24. God damn you Bill and your knowledge bombs I was just recovering from the last few resources you shared last time I was here about Microsoft’s report and how Google and others were exploring search intent for name entity queries, This one however is one to watch, it’s also interesting if you visit wikipedia for a search on Googles list of products where you see a request, as always Bill while I might not fully grasp the concepts fully it’s always enlightening to drop by cheers

  25. Hi Alexandr,

    I admit I was surprised when I started reading about Audio watermarking and cross device tracking; I felt I had to share, it is a bit of a change.

  26. This has been superb blog write-up… Very informative & replete with innovative thoughts… I really like the way you have dressed it up… keep sharing more & thanks a lot!!!

  27. Hi Bill ,
    Thanks for the information . I currently know about this technology what google work on that .
    Audio watermarking and cross device tracking hopefully will be counted as good algorithm in future.
    Interesting Article I must say… well done

  28. Hi Bill,

    It’s scary what Google is doing should this ever come to pass. Frequencies that we can’t even hear? They’re going to be freaking out dog and cat owners I imagine. It’s enough with their Penguin update already now I came across this. What’s next with Google. I wonder what it will look like in 10 years from now.

  29. Hi Andrew

    It’s really interesting that Google might be able to capture ads that are running on the radio and TV, and notice that you listened to or watched those.

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