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Quietnet: Chat client that works over near-ultrasonic sound

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Re: Quietnet: Chat client that works over near-ultrasonic sound

#51

Post by krazydad »

mseebach wrote: post #14
songzme wrote: post #12

Can this be accomplished on mobile devices? This could be a clever trick to implement interesting multiplayer games on train rides, airplanes, where wifi is not available. From a quick research, it seems that iPhones are not able to play ultrasonic sound: "iPhone 4s is rated for 20Hz - 20,000Hz, which means it cannot generate ultrasonic frequencies." - http://stackoverflow.com/questions/10034346/ios-how-to-produ...

I would suspect those environments to be much too noisy for that to work.

Agreed. This particular app starts to fail badly when the AC is on my current room. Airplanes are much, much, worse.

Re: Quietnet: Chat client that works over near-ultrasonic sound

#52

Post by krazydad »

songzme wrote: post #18
songzme wrote: post #15

Just installed and tried all the necessary packages, but for some reason it simply doesn't work. Here's a screenshot: http://cl.ly/image/180b0k3X332g I'm using a retina macbook pro 15 inches

Tried again, this time I get an 'o'. http://cl.ly/image/0e1A2c2i1Y16

Make sure you are in a quiet room (with the AC off). It worked for me on a Macbook retina, but started to fail when the AC turned on.

Re: Quietnet: Chat client that works over near-ultrasonic sound

#53

Post by mcb3k »

katee wrote: post #43
mcb3k wrote: post #20

Earlier quoted context omitted.

Are you sending and receiving on the same computer? I feel like that might cause issues. Are you able to use two separate computers to test?

It actually works much better when sending an receiving on the same computer. It's not as fun though.

Now that I've thought about it more, that actually makes a lot of sense. Thanks for the response!

Re: Quietnet: Chat client that works over near-ultrasonic sound

#54

Post by mbenjaminsmith »

sp332 wrote: post #16
songzme wrote: post #12

Can this be accomplished on mobile devices? This could be a clever trick to implement interesting multiplayer games on train rides, airplanes, where wifi is not available. From a quick research, it seems that iPhones are not able to play ultrasonic sound: "iPhone 4s is rated for 20Hz - 20,000Hz, which means it cannot generate ultrasonic frequencies." - http://stackoverflow.com/questions/10034346/ios-how-to-produ...

Those "ratings" mean the sound will be distortion-free +/- 3dB over that range. You can still make some noise higher or lower than that, it will just be more distorted. I know iPhones support audio formats with at least 96 kHz sample rate, so you should be able to play half that or 48 kHz sounds without too much trouble. It might have some kind of band-pass filter built in, but the ratings won't tell you.

> Those "ratings" mean the sound will be distortion-free +/- 3dB over that range.

No it doesn't. All speaker drivers act as bandpass filters. On the ends of their frequency ranges those +/-3dB points are generally their -3dB points. For most speaker drivers their low frequency cutoff will be caused by the resonance of their motor, dropping off rapidly after that point. The upper frequency limit will be caused by the inductance of their motor's coil with a similar drop off above it.

It's unlikely that the iPhone speaker could reach 48kHz. If you look at expensive high frequency units (tweeters) they'll generally top out at 20-30k. A lot of headphone drivers (which are more similar to what's in the iPhone) barely make it to 20k.

> You can still make some noise higher or lower than that, it will just be more distorted.

Again, nothing about distortion here. A speaker driver will output sound outside of its -3dB points, but, obviously it's going to be much quieter (-3dB is already half as quiet).

Re: Quietnet: Chat client that works over near-ultrasonic sound

#55

Post by nitrogen »

tmp123415 wrote: post #36
namecast wrote: post #8

Earlier quoted context omitted.

Heh, I just visualized my laptop keyboard transposed onto an 88 key piano, and then tried to imagine what a typical vim session would sound like on it...

This must be done.

Many MIDI virtual keyboard apps provide a mapping to the PC keyboard. Install one of those, (e.g. apt-get install vkeybd), plus a softsynth (e.g. ZynAddSubFX). Done.

Re: Quietnet: Chat client that works over near-ultrasonic sound

#56

Post by e12e »

namecast wrote: post #8
GotAnyMegadeth wrote: post #6

Earlier quoted context omitted.

Until you get crumbs under the keys... EDIT: "a wireless, powerless keyboard where every key's click is tuned to a slightly different sound" hang on, like a piano?

Heh, I just visualized my laptop keyboard transposed onto an 88 key piano, and then tried to imagine what a typical vim session would sound like on it...

Obviously Emacs sessions would sound better, as Emacs already is set up to use chords...

Re: Quietnet: Chat client that works over near-ultrasonic sound

#58

Post by e12e »

GrantS wrote: post #34
songzme wrote: post #12

Can this be accomplished on mobile devices? This could be a clever trick to implement interesting multiplayer games on train rides, airplanes, where wifi is not available. From a quick research, it seems that iPhones are not able to play ultrasonic sound: "iPhone 4s is rated for 20Hz - 20,000Hz, which means it cannot generate ultrasonic frequencies." - http://stackoverflow.com/questions/10034346/ios-how-to-produ...

Not ultra-sonic but this app sends photos from iPhone to iPhone using the speaker and microphone. https://itunes.apple.com/us/app/acoustic-picture-transmitter... Fun to play around with and think of the possibilities of using sensors in unintended ways.

Essentially a modem (with zmodem/sz-rz functionality)?

Re: Quietnet: Chat client that works over near-ultrasonic sound

#59

Post by katee »

paulirish wrote: post #49

A webapp using the Web Audio API adopting the same sort of approach: http://smus.com/ultrasonic-networking/

That's really cool! I used the web audio stuff to get real time audio data for interactive visualizations when I did a 5 minute demo of quietnet, the code is available (but might be a pain to get running): https://github.com/katee/quietnet-presentation

Running fully in the browser with visualizations might make a good teaching tool for digital signal processing (although you'd need better DSP code to demo, mine is not a shining example.)

Re: Quietnet: Chat client that works over near-ultrasonic sound

#60

Post by chrissnell »

slowmover wrote: post #10
brownbat wrote: post #2

I'm glad people are realizing that radio waves aren't the only ways to send signals around a room. I really want someone to make a wireless, powerless keyboard where every key's click is tuned to a slightly different sound. Keylogging by acoustic emanations is a well researched technique, I just think it could be a feature if we made the keyboard right. https://www.schneier.com/blog/archives/2005/09/snooping_on_t...

Interestingly, some early wireless TV remotes used sound this way. The battery-free remotes would strike a tone when a button was pressed, and carefully tuned forks in the TV set would resonate in response, triggering the remote function. http://www.tvhistory.tv/1957_Zentih_Ad-Remote1.JPG

We had a tv like this growing up. Whenever the dog would run through the room, his tags would jingle and change the channel. It was funny, too, because the tv channel changer was this rotary dial that was motorized. When you changed the channel, the little dial on the tv would click and spin around.
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