Wicked, well implemented but Id be keen on seeing it on an actual window with conversation to see performance

Awesome hack, really cool. Love it.

Now in the down side… yeah I know… This is illegal to possess in the US.

Also, I seemed to remember seeing something similar here before:
http://hackaday.com/2006/03/22/laser-listening-device/

Beautiful work!

I swear HAD and the supply of junk parts at work have REALLY got me energized towards a couple of different tinkery hacks.

I really have to document and share.
I’m sorry for slacking. :(

you bastard.

Wow old. I think I saw this in one of the engineer’s mini notebooks.

Curtain wall defeats this easily. Interestingly enough some gov buildinhgs in eastern block were build with Curtain walls.

My father was an oilfield tool company executive who traveled to the former Soviet Union on business. He and his fellow execs were sitting in their Moscow hotel playing cards and drinking vodka when he noticed a red laser dot on the curtains.
“What’s that?”
“Oh, don’t worry about that,” said one of the old Russia hands, “That’s just the KGB bugging us with a laser microphone.” And the game continued uninterrupted.
This was about 1981.

When they see the red dot on their window, they might call the police but people would beat me up for less.

Yeah the mims cct was a 386 i believe.. would have to verify that.

Googled the age of the LM386 and the only age reference I found said ‘early 70′s’

this is well know but absolutely unpractical way to spy (that the reason it is known to public). It hard to find reflection (almost impossible for IR) The air is not constant pressure and temperature so it bent and twist laser enough to make it useless for sound carrier. You will be detected soon with viable laser and for Infrared Sun is giant IR projector carrying white noise, as for night fluorescent light emit too much IR to dim any useful signal. Last but not least when was the last time you seen single layer glass window ?

ok.. read the whole post, and it worked eh.. who’d a thunk it :) maybe it was one of those mirror windows.

Pretty low tech for 2010, btw.

The hip kids simply focus the light from any internal light source (in the room) and record the modulated signal of the flourescents [and they ALL use florescents]… I’m leaving an important step out, said the null, but anybody with any physics knowledge can fill it in.

Then you run the signal back through signal processing and get voices back out. Well, voices plus A/C plus random electrical noise plus thermal effects plus so on and so on, which is why real bugs are preferred 12 to 1 by most dentists.

Just about the only thing this crappy tech gets used for these days is listening to in-vehicle conversations, which is why cracking a window… well, who needs that information anyway. You all carry microphones with you now.

However, if you live somewhere people still get it on in cars, you can assemble a lot of spectacularly low quality audio porn. But really, listening to “wait, go slower”, “Ow, that really hurts” and “Did you bring condoms” and my personal favorite “Shhh, did you hear something” was interesting for about a week in 1971.

Then I discovered that it’s way more fun to have a remote controlled air horn (like boaters use) and simply trigger it when the car “steams up and starts rocking”. The first IEOD (instant erectile dysfunction on demand) the world has ever seen* circa 1971 using a filter tuned to CB radios.

Ah, america, how I miss you and your radio shack battery cards.

* barring: crying babies, parents arriving home unexpectedly, olfactory assaults and hearing your mistress say “I got a call from your wife today, Bob.”

Most idiots I know use an iPhone. it is far easier to just remotely turn on its mic and have the phone send you the entire conversation.

So i guess ill keep having meetings in the basement with the radio playing or the vacuum cleaner on.

Heh. Vibrating didlo/toothbrush works well i hear. <3 burn notice.

remember to watch out when working with high powered IR lasers. They can do some serious eye-damage if you aren't careful

I know this works.
But there is a better, not easier, way to decode.
It depends on interference. You have to overlay the original and the reflective beam. Since the movement of the window changes the runtime of the reflective beam, you can decode the sound from this.
I am searchin for plans for this kind of laser mic, but never found them again.

@hubert

not sure if I can post links, but here’s the old Radio Electronics article you’re talking about:

http://72.52.208.92/~gbpprorg/mil/laserl/index.html

@Allen dulles = Excellent troll, It’s a website, but the website links do point to the original magazine articles with construction info.

The last link is an amateur’s wet dream, and not going to yield pay dirt with the junk he’s using… pretty block diagrams, wrong approach.

Let me say this: There is nothing you will think of in surveillance that hasn’t already been thought of, proposed, rejected, reqqritten, funded, hastily prototyped just as the money was about to run out and discarded as useless upon project cancellation – at least three times.

If you can’t het the signals with two or more tunable frequencies in basically real-time to cope with breathing, gas, head shifting and other muscle distractions, it won’t work.

It’s like decoding FSK data using your ears – not a chance of valid data at the speeds required.

The catch with direct interrogation of the voice boxes of biologicals is that it’s useless if they’re not sitting still, you have to basically cook them to do it and the shear amount of dsp that needs to be done to try and pull text out of formants. You’re more likely to interrogate the inner ear of a participant than pull useful speech from the throat of someone. Ever hear a throat mic?

High resolution strobe studies have been done with no results, and the two or three membranes that you can monitor to reproduce sound from are too small to be useful. But let’s say your method was “adequate” and you could chet the membrane and pull sound back out of it…

It’s much worse than the problem of pulling text from muddy speech recordings, as we still need to “point the mic” except under lab conditions. In theory computation can do anything, but in practice it isn’t that good.

Now, imagine that the user is moving in a random hotel room, and you want to do speech capture. Good luck with that, even with a decent scanning device and a static polar map of the room.

Again, cellphones to the rescue here… Cellphones [and a company that shares initials with National Semiconductor who are "the keeper of the keys"] have single-handedly delivered the holy grail of surveillance to anyone with the right connections, or failing that, adequate funding.

BTW, the amount of gear required to correctly sweep and monitor a room using complex heterodyned microwave signals is substantial, and isn’t gonna be available in the wild any time soon.

And – MD – even microwave penetration of walls STILL relies on cell phones or a cavity bug.

I intend on trying this with a green stargazing laser its beam doesnt distort as much as the red laser does