Instructables

How to Listen to Light

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Picture of How to Listen to Light
The human eye cannot discern flicker with a frequency greater than roughly 30 Hz. A light turning on and off faster than this does not appear to be turning on and off. Instead it appears to have a constant intensity to the eye.

Human ears however are much faster, that is, better able to perceive a signal changing quickly in time. The human ear can detect frequencies from roughly 20 Hz to 20 000 Hz, provided those frequencies arrive as sound.

Now suppose there were an easy way to change light of time-varying intensity, into sound of time varying intensity. Then you could "hear" light that was flickering too fast for you to see it.

The humble silicon solar-cell can convert a time-varying light signal into a time-varying electrical signal. This small electrical signal can then be fed to an audio signal amplifier and converted into sound.
 
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Step 1: Parts:

Picture of Parts:
1 audio amplifier (Radio Shack Catalog #:277-1008)
1 1/8-inch (3mm) headphone plug, can be mono or stereo
1 small Silicon solar cell with approximately 1 cm2 in area
1 1/2-inch PVC pipe cap
some wire, solder, epoxy, black paint, etc.

maker125 years ago
I did this once a IR remoted played part of the twilight zone theme song! it is landing!
Thumbs down, everyone! I don't think they would do this!
(removed by author or community request)
Actually this guy posted his about 3 years prior to your ible'
WHAT DID YOU SAY???

Just Kidding...but mine uses headphone:)-
Dr.Bill2 years ago
Would be Very Interesting to listen to Modulated Laser Light.

Maybe even have 2 way line-of-sight laser communication.
Thanks...I had really wanted to record the sound my light listener made but had no time...
Jack A Lopez (author)  blinkyblinky2 years ago
I'm glad I could help! Thanks for noticing this 'ible.
You're welcome...but...THIS IS EXACTLY MY CONCEPT!!!!
Geoffrito5 years ago
whoa, that's interesting. Who'd have thought that candles secretly play music?
Now people can sell battery powered tea light candles for privacy concerns, to help confuse laser window monitoring bugging equipment!

Although it won't work well against the good optical bugs because a technician will just tune out the frequency of the tone generated tea light music.

Can I get an LED that plays the theme from "Get Smart" please?
Dunt da daaa DA!
Dunt da daaa Duh!
Klaudiuszm3 years ago
I made one of these with a broken solar light. I figured it would have a nice enclosure and well, it was the only panel I had in my house.
Jack A Lopez (author)  Klaudiuszm3 years ago
That works. Or at least I'm guessing that it worked... Have you found any interesting sounding light sources?
Yeah I have. remotes are always fun. plus my glade air freshener light. I had also built a http://www.instructables.com/id/Music-LED-Light-Box/. I found that you can attach it for some visible fun. :D
rcisneros3 years ago
Actually you are half right.
They are prob using the music chip as a template that produces a smooth flicker cycle they have tons of.
The second part is because our brains naturally like certain sounds, patterns and tones. We change them over time, but there is a larger portion of these tones and patterns in classical music. I believe Bach is the winner in that category.
In that way flicker would cycle would be more pleasing.
theGpayne4 years ago
hey, would it be possible to use a solar panel from a calculator? would i just hook up the cables on that directly to the 3mm plug?
Jack A Lopez (author)  theGpayne4 years ago
Yeah.  I think that would work.  You should try it, and see, I mean hear, what it does.

BTW, I think the solar panel from a calculator is typically 3 or 4 cells wired in series.  See picture.  That fact might be important, or it might not be.
calculator-solar-cell.png
Loolykinns5 years ago
dont you have any live sample of the output? I'd love to hear whats the output
Jack A Lopez (author)  Loolykinns4 years ago
For those of you who asked for sound samples for the "How-to-Listen-to-Light" 'ible, I have added a last step with a number of .wav files attached to it.
(http://www.instructables.com/id/How-to-Listen-to-Light/#step9)
Kiteman5 years ago
Flickering LED "candles" also often play "Happy Birthday", even at Christmas. The mass-produced chips from musical cards are stupidly cheap when bought in factory-scale bulk.

Somewhere (SciToys?) I have seen this idea as half a laser-communicator. A microphone is used to add a flicker to a laser pointer's beam, which is focussed on a distant solar-cell, and an amplifier is used to turn the flickering output back into sound. Not hi-fi, but cool.

It would also be cool if you could post some mp3 or wav files of different sounds you have produced - what does that version of Fur Elise sound like? How annoying can a strip-light be?
Jack A Lopez (author)  Kiteman4 years ago
For those of you who asked for sound samples for the "How-to-Listen-to-Light" 'ible, I have added a last step with a number of .wav files attached to it.
(http://www.instructables.com/id/How-to-Listen-to-Light/#step9)
Unit042 Kiteman4 years ago
Yes, I first saw it on scitoys too. Sound amplitude modulated laser light. (Intensity of light followed that of the sound source's wave)
Unit042 Unit0424 years ago
Um, "it" as in, the laser communicator.
Very nice job Jack maybe add a mp3 ... wondering what a black light sounds like....My son made that Kite and it works best with radio or a resistor before the laser for voice unless you buy a very good laser (not the flea market $1.00 ones), don't use indoors with fluorescent lights you hear static( from the tubes flickering 100-120 times a second I think)...years ago I had a client that said the lights talked to her and I did like Jack to show that they did talk and she wasn't crazy .....Kite strip light = fluorescent?
Yes, strip-lights = fluorescent. They do flicker at around 100-120 Hz (twice the quency of your supply, apparently), which is why they can cause headaches - your eyes try and adjust to the flicker but can't keep up.
Yes, this is one of the reasons they now put 3 bulbs in office fixtures (at least here in the USA) on different circuits, attempting to cancel out the "flicker to headache effect" :-)
robcull4 years ago
Fur Elise??

Really?

Can you post a video recording of this sound?
Jack A Lopez (author)  robcull4 years ago
For those of you who asked for sound samples for the "How-to-Listen-to-Light" 'ible, I have added a last step with a number of .wav files attached to it.
(http://www.instructables.com/id/How-to-Listen-to-Light/#step9)
mskogly5 years ago
I wish I had discovered the secret music in the tea lights, that is really cool.
scafool5 years ago
If I put this on a telescope would I be able to hear little stars twinkling away in the night?
chalky5 years ago
cool!
Sweet Instructable, I want to do this so I can tell my friends how cool I am listening to light. ;-) +5/5 stars.
A good name5 years ago
Ooo... how about we make a model titanic and leave the candles on so that it's like the band is still playing!
A good name5 years ago
Ooo, next time teach us how to listen to god! That would be soooooooooooooooooooooooooooooooo cool... In fact, I'll make an instructable about it RIGHT NOW! 1: Build giant Radio antenna/transmitter/receiver dish 2: Insert the receiver dish into a speaker 3: Insert the transmitter dish into a microphone 4: You may now talk to god, it may take a while to get the right frequency, and you might need to change around the battery power, but other than that, it works great.
There could be subliminal messages in my LED tea lights!!! Oh My GOD!!! thats kicka**.
lol
cprocjr5 years ago
wow i didn't know they played music. amazing.
cool, i have that same amp from radio shack, i think i'll do this when i get a chance
alexhalford5 years ago
The idea is pretty good but the thing I was most impressed at was how the instructible was put together, no missing steps, very well explained. Very good in my opinion.
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