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The Daredevil Camera

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Re: The Daredevil Camera

#31

Post by FreeFull »

nxzero wrote: post #21
Artlav wrote: post #18

Earlier quoted context omitted.

Not exactly unheard of, but quite rare. I found a company that made large arrays like that, but they seem to operate in near field, measuring only the sound volume. Imagine a wall of microphones next to a truck - you can tell which part of the wheel makes the sound. That sort of stuff. As for an actual "camera" that turns sound into an image - i've never heard of one.

Isn't this exactly what sonar does? SOund Navigation And Ranging: https://en.m.wikipedia.org/wiki/Sonar

Sonar sends out sound and then listens for the echoes though, rather than just take in sound from other sources.

Re: The Daredevil Camera

#32

Post by Artlav »

bcherny wrote: post #30

This would be pretty powerful if you combine it with speech recognition. If you put this array in the middle of a crowded room, can you better tease apart different audio sources?

Ironically, this thing can't record sound as we know it - it only have enough buffer space for a few hundreds of samples per mic, 30 times per second. They are to be FFT-ed rather than continuously recorded.

While such a contraption should, in theory, be able to distinguish between dozens of voices in a room, it would take much, much heavier signal processing to achieve.

Re: The Daredevil Camera

#33

Post by sbierwagen »

ProAm wrote: post #27
Artlav wrote: post #18

Earlier quoted context omitted.

Not exactly unheard of, but quite rare. I found a company that made large arrays like that, but they seem to operate in near field, measuring only the sound volume. Imagine a wall of microphones next to a truck - you can tell which part of the wheel makes the sound. That sort of stuff. As for an actual "camera" that turns sound into an image - i've never heard of one.

Doesn't the army use something like this in the field to determine enemy sniper locations when they are taking pot shots?

https://en.wikipedia.org/wiki/Gunfire_locator

Re: The Daredevil Camera

#34

Post by jsprogrammer »

bcherny wrote: post #30

This would be pretty powerful if you combine it with speech recognition. If you put this array in the middle of a crowded room, can you better tease apart different audio sources?

If you have more than one mic you can begin to triangulate sources (you might be able to use a single mic if you know the geometry of the room and/or could send out noises), so it would definitely be possible.

Consider that most of us are carrying around multiple, networked mics. Some may already do it, but I doubt it will be too long before everyone can virtually tour real-life spaces and visualize the sounds there in real-time.

Re: The Daredevil Camera

#35

Post by radiowave »

rev_null wrote: post #6

The timing issue between the microphones doesn't surprise me. Multi channel soundcards require a single ADC that processes all of the channels in unison (same for the DAC). This is also why you can't just plug four stereo cards into a PC and expect it to make an 8-channel system.

Strictly, multiple ADCs are fine, but what matters is that they are all locked to the same sample rate clock, connected to each card either via a digital audio input (e.g. SPDIF) or a dedicated clock input (e.g. word clock).

Re: The Daredevil Camera

#36

Post by Qworg »

nxzero wrote: post #21
Artlav wrote: post #18

Earlier quoted context omitted.

Not exactly unheard of, but quite rare. I found a company that made large arrays like that, but they seem to operate in near field, measuring only the sound volume. Imagine a wall of microphones next to a truck - you can tell which part of the wheel makes the sound. That sort of stuff. As for an actual "camera" that turns sound into an image - i've never heard of one.

Isn't this exactly what sonar does? SOund Navigation And Ranging: https://en.m.wikipedia.org/wiki/Sonar

There ARE sonars that deliver an image.

http://blueprintsubsea.com/starfish/images/sonar/452/sf452_s...

That's just one example - look for side scan sonars for the earliest stuff (https://en.wikipedia.org/wiki/Side-scan_sonar) or sonar imaging for the latest stuff (http://www.tritech.co.uk/product/gemini-720i-300m-multibeam-...)

Re: The Daredevil Camera

#37

Post by radiowave »

morsch wrote: post #20
rev_null wrote: post #6

The timing issue between the microphones doesn't surprise me. Multi channel soundcards require a single ADC that processes all of the channels in unison (same for the DAC). This is also why you can't just plug four stereo cards into a PC and expect it to make an 8-channel system.

You can't? I'm sure I tried multi-channel via separate sound cards and it sounded fine to me. Maybe I was lucky with the timing, or the audio subsystem somehow accounted for it?

Depending upon what you're using it for, you might well get away with it, but for some purposes the accumulated sample rate clock drift eventually gets too bad.

You could make a long multitrack recording this way, and so long as you played it back from the start on the same hardware (i.e. so the soundcards would drift relative to one another more-or-less consistently with how they drifted during the recording), the playback might be ok. But if you begin playback half way through the recording, then the timing between channels might be out, as your software has no idea how much drift each channel ought to have accumulated by that point in the recording.

Mind, it's been at least 15 years since I actually put any of this stuff to the test. Tolerances on modern soundcards might be really tight.

Re: The Daredevil Camera

#38

Post by Qworg »

yathern wrote: post #26
nxzero wrote: post #21

Earlier quoted context omitted.

Isn't this exactly what sonar does? SOund Navigation And Ranging: https://en.m.wikipedia.org/wiki/Sonar

No. SONAR sends out an ultrasonic ping and times the response of its echo to get a distance. This project is similar in that it involves visualization from audio, but apart from that, it's quite difference. This is the ability to see a sound. To derive the positions of arbitrary sounds in a viewing plane, and render it like you would a picture or video.

He's still driving the scene - illuminating it, if you would.

Re: The Daredevil Camera

#39

Post by dragonwriter »

colechristensen wrote: post #28
nxzero wrote: post #21

Earlier quoted context omitted.

Isn't this exactly what sonar does? SOund Navigation And Ranging: https://en.m.wikipedia.org/wiki/Sonar

No. Most sonar is active (sends out pings) and has only one input (one microphone) It builds pictures by directing the ping and measuring time until the response. This is fundamentally different than an array of microphones passively listening to, and creating a fine grained picture of some sound source.

> Most sonar is active (sends out pings) and has only one input (one microphone)

While I believe the US Navy doesn't prefer the term "Passive Sonar", submarines and some surface ships are equipped with hydrophone arrays (either on the hull, or towed arrays, or both) as well as active sonar; this isn't an uncommon thing. (I was under the impression that the active sonar didn't use a single hydrophone, but instead used the same hydrophone array used for passive detection.)

Re: The Daredevil Camera

#40

Post by soheil »

I think the whole thing could be done pretty much all in software. Setup a bunch of phone numbers in Twilio, using a bunch of your friends iPhones, strategically located, call the numbers and process the data using Twilio API. Whatsapp or other real-time voice communication apps with an API may work too.
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