Have you ever needed to hear a conversation in a room you are unable to access or bug easily? If so, and if that room has a window, you can using a laser microphone.

A laser microphone is a device that uses the vibrations of a window or similar pane of glass or plastic to record sounds near said window. A laser is pointed at a window and a photocell is placed where the laser's reflection lands. That photocell is then connected to a recording device. The vibrations of the eindow causes slight movements in the laser's reflection which, in turn, cause small fluxuations in the photocell microphone's current. This may seem complicated but it can be done cheaply and easily.

Step 1: Things Needed

Picture of Things Needed
The things you need for this build are very easily obtained and cost me about $10.

Soldering gun( or just electrical tape if you're being really cheap)
Scissors( if you're using headphones)

A laser pointer $1.50
A photocell $.30
A bad pair of headphones or, as I used, a speaker cable ending normal headphone jack $3.80
A tripod $0.00( already had one and isn't needed)
Recording device or computer with recording software
daqinhuqi1 year ago
vjackson41 year ago
its working with an led
but wen i connected a speaker to the breadboard its not givin any reply
Also can I just plug the cord into a speaker so I can hear it ?
bioboy725 (author)  shaggydoo1212 years ago
In all honesty I am unsure. I had trouble when testing this and rushed to enter it in a contest. This instructable is practically unfinished and I have been meaning to remove it until I have had the time to fix it. Sorry for being unhelpful.
Please explain placement of the photocell . I'm new to this and want to build one but first I need to understand it.
Couldn't you pull an infrared laser diode out of an old cd drive?
I just got in a 480mw IR laser to try one of these. Will be making a guide as I do It. I have worked with the real thing once before I retired form law enforcement. Aiming the IR lasers are the fun part. We used a digital video camera but your phones camera can see IR qlso.
50-503 years ago
I am so anoyed at you for beating me to this idea, I was going to enter this but needed to order more photocencors.if you could better explane how this works you have a very big chance of winning.
Ian01 50-503 years ago
You might beat this if you find a way to make it ignore ambient light. (Hint: TV remotes do it.)
bioboy725 (author)  Ian013 years ago
One of the last steps already mentions infrared lasers. I just didn't have the time as I was going on a school trip and couldn't wait for the stuff to be shipped.
Ian01 bioboy7253 years ago
I didn't mean lasers. I meant modulation.
bioboy725 (author)  50-503 years ago
Well thank you for the feedback. I knew someone else would have the idea so I kind of rushed it. I bought everything that day and did it all quickly. I am working on improving the instructions now so I hope that helps.
Tanmay Das3 years ago
You can also use an infrared laser and receiver instead of ordinary laser.
IR is invisible to the naked eye so you won't get caught and also any other outside light will not interfere with the receiver.
bioboy725 (author)  Tanmay Das3 years ago
I mentioned that at the end but I was rushing to get this up before anyone else could, so it was poorly worded.