I read a similar article several days ago and came to the same conclusion that you did - this is very sophisticated. Maybe too sophisticated. Which made me wonder whether this is theoretical "in the lab" by researchers or actually out in the wild. As for dogs hearing it? sure - maybe. There are lots of noises. My furnace fan makes a blowing air sound. I don't howl because of it - it's just annoying white noise that I ignore.
Need a Raspberry Pi project to listen for this. Then becomes a keyfob that you carry with you that blinks when these secret US signals are detected.
At the time I wasn't able to find links to the actual work - just blog posts that circularly reported on this subject from each other. The quote "ultrasound cross-device tracking (uXDT), [..]. deployed in modern-day advertising platforms" -- really? like what and who?
The link to c3subtitle.de has vague statements in it too "newly-founded company faced the nemesis of the security community and the regulators (e.g., the Federal Trade Commission)" Really? Who?
The underlying premise that I have a phone near my computer that is listening to a beacon played by Ads seems incredulous. The idea that an ad agency would go to these lengths for such a brittle system is surprising. It would have to work "often" to pay off --- and for what gain that GeoIP doesn't provide today? What is that extra 1% that they are after? Plus in this day of auto-playing videos I have my audio muted (or headphones plugged in) - which I think many others do as well - or at least the volume is low. This again closes the door from an ad viability perspective. I get that advertisers want to link my laptop to phone to tablet together so that they can track Me! But there are other ways to do this already (FB beacons for example) that aren't as brittle.
While I appreciate Raising the Alarm - I doubt that (say) Google Ads is doing this. Sure -- maybe some govt spy agency is using this technique to spy on people (i.e. break through Tor). Yes I believe that. If I was a criminal I'd wrap my head and devices in tinfoil.
I'd like to see more evidence that advertising networks are actually doing this.