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Comment by weinzierl | Hacker News Reader

> Yan was even able to embed an ultrasonic version of the Rick Astley song “Never Gonna Give You Up,” which became audible at the point where the two signals crossed.

At 33C3 I rode an escalator when I suddenly heard "Never Gonna Give You Up" but apparently no one else did. It was over after a few seconds. At the top of escalator there was a guy pointing a directional speaker at random people.

Only reference I could find is in German, but it has a picture [1]. The story says the guy on the picture is not the inventor of the device.

EDIT: The thing is a parametric ultrasonic speaker and the design files and software are on GitHub [2].

[1] https://motherboard.vice.com/de/article/784z74/33c3--hacker-...

[2] https://github.com/niklasfauth/parametricspeaker

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It's actually off-the-shelf tech now. I've been in a number of supermarkets where they use this to beam ads at you while standing in line for the checkout. (All of which have since stopped doing it, for what it's worth. YMMV.)

There was some hope for a while that this might turn out to be a way to hack sound so that you could produce a flat speaker full of those tiny ultrasonic speakers, and then use non-linear interference to produce deep, booming bass sounds, without having to have the much-larger speakers you need today for that to work correctly. Unfortunately, either nobody could crack the technique, or it's simply impossible, because the real speakers that emerged are quite tinny. Here's a commercial offering, where they're only willing to promise down to 150Hz in the text: http://ultrasonic-audio.com/acouspade-technical-specificatio... "The sound is of high-quality, with low noise and great frequency response, which includes authentic reproduction of bass notes and frequencies as low as 150 Hz." Which, if accurate, is better than the speakers I've heard, but still a long ways from "thumping bass" coming out of a square that could be hung on the wall as casually as a picture frame.

>I've been in a number of supermarkets where they use this to beam ads at you while standing in line for the checkout.

This is more than creepy. It should be made illegal along with using cameras for anything else than security.

I would have thrown a bigger fuss if they didn't disappear as quickly as they did. I assume other people threw a fuss for me, for which I thank them, whoever they are.

The f'ing stupid thing is that the checkout line is already one big ad. It advertises all the things that the stores have already figured out you're likely to buy at the end of a shopping trip; candy, drinks, SD cards (dunno why but it's pretty consistent), etc. It is the most effective possible ad, since everything it is advertising is literally within arm's reach for immediate purchase. You'd think that would be enough!

I think the SD cards might be more about discouraging shoplifting of a small easily liquidable good.

What we really need are highly tunable and directional EMP generators, which can be easily concealed. You could “solve” everything from annoying drones, to people listening to Peppa a pig on their iPads, through the speaker.

Of course you could also fry a car’s ECU, but um, swings and roundabouts right?

If you think that's creepy, imagine it with good voice synthesis along with a voice profile of yourself. I wonder if they could get close to making it sound like your internal monologue saying "I should buy that impulse item in front of me"?

recent new improvements in voice synthesis could make this happen soon enough tbh.., capture you speaking in the super market, filter your voice out, then beam that shit in. i like the idea :D i can already see us all comming home... why the fk did i buy this milk, why do i keep drinking this milk.. wtf :D (paranoia 1.0) wonderful world!

Why should the supermarket playing any sort of music on any sort of speakers they want inside of their own building on private property be made illegal?

Who is it harming? Is your association with the supermarket not entirely voluntary?

I think this is a subject of 'customers rights' or something like that, depending on the country. You cannot call yourself a store and do whatever you want inside it because it is yours. Maybe this music/ad is legal (or legally uncovered) for now, but customers are definitely the source of the entire business and have a right to have rights.

You could produce that deep bass if you knew exactly where the listeners are. Throwing some computer vision/ML in the mix could solve the problem.

PS: It can't be patented now, cause I mentioned it on HN first :)

Haha! What if we had a website where people could post such ideas and discuss them? The process of discussing and refining an idea would make it un-patentable?

That would be an interesting forum for geeks / problem solvers AND would kill stupid/obvious patents as a side effect, and act as a repository of prior art!

Since such discussions might articulate at least the broad ideas (even if they don’t get to a specific implementation) this might discourage at least overly broad patents.

PS: Did I just make this idea un-patentable by anyone else? :D

It exists! http://www.halfbakery.com/

Hmm... thanks for that link! That website says nothing about patents and prior art, so its purpose seems somewhat different. Shouldn’t takeover someone’s website meant for something else :-)

Unfortunately that is now how patents work.

"You could produce that deep bass if you knew exactly where the listeners are."

I'm unsure what you are trying to say. The problem with deep bass, as far as I know, is not that it only works in certain places; it is that it can't do it at all. See the frequency response chart in the page I linked, which I suspect if anything is probably overselling its bass capabilities. As I said, I don't know if it's merely that nobody has cracked the problem, if it is somehow fundamentally impossible with this technique, or I'll add a third one here, if it's possible but impractical (i.e., "requires a 100x larger piezoelectric array" or something).

If you've really never heard one, they have a very characteristic tinny sound. Usually when you have a conventional tinny speaker, the speaker has a relatively narrow range and is missing both the low and the high ranges. With the ultrasonic speakers, the bass is entirely gone, but the response up through the higher frequencies is pristine pretty much all the way up the human range. So you get voices with no bass at all, but that are extremely, extremely clear and easy to understand because all the higher harmonics are intact, if not outright emphasized. Very distinctive sound, even if you don't notice the highly directional and sharp sound immediately the acoustic signature is unmistakable.

The trouble with bass is you get the product of two factors both working against you.

First of all, to produce a sound that is identically loud to the human ear, the sound wave pressure amplitude has to increase tremendously as you go down in frequency. At 40 Hz, which is not very deep bass, you're talking a 40 dB SPL increase necessary over 1000 Hz.

Furthermore, as the frequency drops, the sound waves become longer, meaning that with constructive interference, the volume of space in which you have to produce significant sound pressure increases with the inverse of frequency.

Taken together, this means that at 40 Hz, this type of speaker must output 16*25 = 400 times as much sound energy as at 1000 Hz. To reach deep bass territory of 20 Hz, you're looking at a 1600 times increase in the energy required.

I remember reading about this in Popular Science when I was eleven years old. They compared it to the difference between laser light and conventional light.

I had a Yamaha soundbar some years ago, which could be calibrated via a small microphone, that you would place in the location in the room, where you wanted the sound to be beamed. During calibration it would create some beeping and whooping sounds, I guess to learn about the room it was in and you could then sort of have a sound bubble in your sofa, when watching a movie late at night.

That sounds pretty similar to Sonos Trueplay: https://www.youtube.com/watch?v=8QgJHUy93T0&t=138s

Yes, the sound emitted from the soundbar during calibration was almost the same sound as in that video.

"Never attribute to stupidity that which is adequately explained by malice."

I NEED to buy one of these immediately! (at various points my two oldest kids have rick-rolled me and it's pay-back time).

You can build one yourself if you want:

https://hackaday.io/project/9085-ultrasonic-directional-spea...

Its reasonably well known tech in the maker community these days... I first saw one demoed at a Dorkbot meeting 10 years or so ago.

I was actually just digging through the Github project to see what it would entail.

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