h a l f b a k e r yI CAN HAZ CROISSANTZ?
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Sunbeam glitter microphone
Hear the sound of the performance as if you were at any part of the venue little dustlets vibrate to the music while a laser microphone measures their movements the particulates throughout the room as well as particular areas at the stands each is an addressable audio receptor | |
little precisely shaped particles drift through the light glittering with the vibration of the rooms sound
A laser pointed at these particles detects their vibration then the computer translates this as sound
You can hear what the music would sound like anywhere at the venue from the front rows
to the stage
frequency response to bass just goes with linearized particle arrays rather like a wide array radiotelescope
(if lasers can zap mosquitos out of the air they can colisten a group of particles)
Particle image velocimetry
http://en.wikipedia...e_image_velocimetry
Usually used for flow visualization [csea, Jul 01 2010]
The Secret Life of Dust
http://www.bookpage...cret_life_dust.html
Plenty to go around, some difficult to image at a distance [csea, Jul 22 2010]
Laser microphone
http://en.wikipedia...ki/Laser_microphone
Need large surface like wall or window . [Cedar Park, Jul 23 2010]
[link]
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I did some research a few years ago on almost exactly this idea, using PIV [link], and a related technique called laser doppler velocimetry [LDV]. |
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It turns out that the actual particle displacement of sound is extremely small, and is inversely related to frequency. For example, a 100dB SPL tone at 100Hz has a displacement of around 32 microns, and at 200Hz, this reduces to 16u, etc. At 6400 Hz, it's 0.5u, a pretty tiny distance to image reliably at 10m or so! |
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Then, consider that for reasonable fidelity, one would also need to resolve 16 bits of amplitude below our 100dB reference, or around 7x10^-12 meters. (for comparison, An angstrom is only 10^-10 meters!) |
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Also, the "near dc" component of airflow in rooms (drafts, convection) dwarfs the audible component of interest. |
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So this would take highly stable optics on an optics bench to work at all. I gave it up as impractical (which is why it's decent halfbakery material...) + |
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Sadly, because of the particle-choked air, the lasers only pick
up the sound of people sneezing. |
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Most indoor air is full of plenty of particles of dust, soot, pollen, etc. No need to add anything! |
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[Edit] It would simplify the imaging software significantly if a cloud of uniformly suitable-sized particles were pumped into the space to be measured. Popcorn oil, anyone? |
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[Edit2] I've just finished a really great book on dust, well worth the read [link2] |
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//Mosquitoes are the size of many particles clumped
together// The SI unit for the size of a particle was based on
a single Lichopodium spore, under a bell-jar in Paris,
reverentially taken out and cleaned once a year.
Unfortunately, last year the technician sneezed; we no
longer have a standard, and the size of a "particle" is
undefined. So [21_Quest]'s assertion is, regrettably, no
longer correct. |
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I like, but how do you compensate for Brownian motion? [+] |
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From [Cedar Park]'s linked wikipedia article:
//A new type of laser microphone is a device that uses a laser beam and smoke or vapor to detect sound vibrations in free air.//
Now we know why that bloke in X-Files was always smoking.
Or do we? |
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