
High-Tech Window Cling is Like a Volume Knob for Real Life - gmatty
http://gajitz.com/high-tech-window-cling-is-like-a-volume-knob-for-real-life/
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ohazi
Created by an industrial designer, not an engineer. From the designer's
website [0]:

> With its concentric broadband antenna rings, it harvests the energy of
> electromagnetic noise from Wi-Fi, and similar signals and this way also
> reduces the level of e-smog pollution in your environment.

 _facepalm_. This is nonsense.

[0] [http://id2studio.at/content/noise/](http://id2studio.at/content/noise/)

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wavesounds
I think more likely this was made by some film students for a school project
or something then by physicists with a working prototype.

I always thought the only way of doing this would be to have detached
microphones positioned between the speaker and the target noise so the system
has enough time to compute the inverse of the incoming waves and send them out
with enough space to cancel in the correct phase.

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mweil
Does anyone know where to follow this project, or perhaps if there's a
Kickstarter or something? I can't seem to find anything outside of this one
article. I would pay very good money for something like this. Ground floor
apartments on major streets are awful. :-(

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pallandt
Yes, this should be on a crowdfunded project asap if the prototype in the
video was really functional and no simulated sounds were added. I'd buy it in
an instant! Maybe I'll attempt to promote it on Reddit to help with gaining
more 'mass-appeal' traction.

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chm
I'm pretty sure it was CGI.

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darkmighty
Yes, and there's whether it actually works IRL. I think it's feasible to have
something like the concept, but there are quite a few hiccups along the way --
I'm no audio expert, but I suspect that a single microphone/speaker location
may be unable to cancel satisfactorily the incoming sound field through the
window. Also, Loud noises creep in through various places, so if your window
is quite good already you many not get much improvement.

But a good concept and hard work (and hope) usually lead to quite good
products...

I.e. noise cancellation in building is usually approached through "get better
insulation", not through the plausibly cheaper "let's spread a speaker/mic
array inside/outside to cancel what's coming form outside".

~~~
msandford
I've done quite a bit of signal processing in my day. Audio, image/computer
vision, radio comms, etc. This product strikes me as not terribly honest for a
few reasons:

Geometry

The mic/speaker assembly are in the middle of the window but the window has
substantial size relative to the dimensions of the room and the distance the
listener is from the device. What this means is that you have a multipath
problem; the original sound can come through the whole window (even the wall!)
but the canceling sound can only eminate from the speaker.

If you draw a straight line from the original noise source, through the device
and from there it happens to head towards your ears, this can work. If not
things will get jumbled up and it might cancel or it might actually reinforce
the noise, rather than cancelling it.

[http://en.wikipedia.org/wiki/Loudspeaker#Directivity](http://en.wikipedia.org/wiki/Loudspeaker#Directivity)

Physics

A speaker is a device that works as a derivative of the original signal. That
means it needs some amount of "advance notice" of the sound in order to be
able to create the proper pressure wave to cancel out said sound. The "advance
notice" is usually done by means of some distance between the microphone and
the speaker but the device is very thin. Worse, the amount of "advance notice"
depends on the frequency of the sound which generally makes it an intractable
problem to solve for the transient case.

[http://www.customanalogue.com/elsinore/elsinore_19.htm](http://www.customanalogue.com/elsinore/elsinore_19.htm)

So what people do is focus on periodic noises like hum, hiss, buzz, rumble,
what-have-you. In this case you don't need to make sure that any one peak has
it's inverse reproduced perfectly, you only have to ensure that ONE peak is
cancelled out by SOME OTHER out of phase peak. If it takes a couple of cycles
for the computer to catch on, no big deal that's just a bit of start-up noise.
Bose headphones don't IMMEDIATELY make the plane quieter, they just do it so
fast that you don't notice the amount of time it takes for the system to warm
up. It seems instant even though it's not.

But what this means is that a bunch of the sounds being cancelled out probably
wouldn't be cancelled out quite so nicely as a lot of them are transients like
the bottles breaking or the construction site or the park.

I'd really love to be wrong about this. There's a joke that goes "An engineer
will tell you it's impossible until you show him how to do it. Then he'll say
it's obvious." It's entirely possible that this guy has figured something out
that the rest of us haven't. But I will remain skeptical until I can actually
put my hands on one and benchmark it for myself

~~~
dustcoin

        The mic/speaker assembly are in the middle of the window
        but the window has substantial size relative to the
        dimensions of the room and the distance the listener is
        from the device.
    

For what it's worth, the pictures in the article show a series of rings around
the device that significantly increase its surface area, a component that is
not present on the device in the video.

~~~
msandford
Yeah I'm not optimistic about those. They're clearly too small to be
electromagnetic drivers (think magnets and coils) so best-case they're active
piezo devices that are epoxied on (need to have a good bond) turning the whole
window into a radiative speaker. Sadly those are limited to high frequency
sound only (several kHz and up) so they wouldn't do much good for anything
other than perhaps the bottle noise.

[http://en.wikipedia.org/wiki/Loudspeaker#Piezoelectric_speak...](http://en.wikipedia.org/wiki/Loudspeaker#Piezoelectric_speakers)

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eps
This is an obnoxious designer BS, this is just not doable for a host of
reasons - from basic physics to unavailabilty of algorithms required to the
lack of physical components liberally massaged into the rendering - so it's
even more fascinating to see the HN thread filled with "take my money" and
"awesome" comments.

Really, fellas? I don't mind a discussion on how it could possibly be done,
but where's your rudimental critical thinking? Even reddit had a better
discussion [1].

[1]
[http://www.reddit.com/r/gadgets/comments/1pdfb0/volume_knob_...](http://www.reddit.com/r/gadgets/comments/1pdfb0/volume_knob_for_your_window_sticks_to_glass/)

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chad_oliver
I'm not convinced about the ability to block out certain _types_ of sounds
(e.g. birds vs traffic), but blocking out certain frequencies should be quite
possible.

Of course, there's one question the article didn't address: what proportion of
sound is actually transmitted through window panes? One would expect that a
whole lot of low-frequency sounds (traffic) would come through the walls too.

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radley
I got the impression it would play bird sounds, i.e. a "zen" noise generator,
not filter actual bird sounds through.

~~~
tempestn
That's certainly more realistic, but I think it was pretty clear in the video
that the device identified the various types of sounds coming from outside,
and allowed the user to independently control the amount of each to be let
through.

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bigtones
This is complete and utter fiction.

~~~
GhotiFish
well... Maybe not _complete_ fiction. Almost total fiction I would say.

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oakwhiz
Selective noise cancellation could be possible using a Fourier transform. Zero
out the coefficients that you still want to hear and then perform an inverse
transform, then a time-domain inversion, and finally apply the appropriate
amount of delay to the signal.

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chas
You might know this, but I want to state it at least for the benefit of people
reading this without much signal processing experience. Just zeroing like that
really isn't the best idea. Square waves (that are 1 for signals that you want
and 0 for signals you don't want) inverse Fourier transform to sinc
functions[1], so if you are filtering just by chopping things out, it will
greatly distort the time-domain system because the inverse Fourier transform
of the filter and the signal get combined (convolved) in the time domain.

[1]
[http://en.wikipedia.org/wiki/Sinc_function](http://en.wikipedia.org/wiki/Sinc_function)

~~~
msandford
Yeah exactly right. If you don't make it smooth in the frequency domain it
won't be smooth in the time domain either.

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brianbreslin
Does anyone remember those suction cup speakers that attached to windows and
turned them into speakers?

Years ago I wanted to splice a noise canceling headphone into one of these
devices and make the windows noise canceling. Would that even be feasible?

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dromidas
I totally hate active noise cancelation... I don't know whether it only gets
out like 99% of the noise while leaving like... the outlines of a clipped out
picture on photoshop or what, but it's hell on my ears. It just causes pain
without any indication of whats causing it and that's incredibly unnerving.

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swalsh
I looked into noise cancellation technology a while ago, because I have a
hobby woodshop, and I want to be able to use my tools past 10 pm.

I just don't believe this concept could work the way the video demonstrates
it. Nice interface though... but that's kind of the easy part.

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garthdog
I'll believe it when I see it...

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jreed91
That was a fantastic video.

