Thanks to Jared for sending in his cool project! Check out the full build on Instructables.
So, first off.
This instructable was a LONG time coming. I had come up with this idea a while ago, after hearing about the details behind some basic “speech jamming” anomalies that occur when people use intercom systems. Basically, the intercom would introduce an ever so slight delay to the output of the speaker, so you would end up hearing an echo. I had planned on making this many months ago, as I previously stated but I was going to try and go discrete, aka, use a micro-controller and attempt to program some sort of delay code. But alas, I never could figure it out.
Then I found out about a very, very neat little IC, the PT2399. This thing is the heart of this circuit, and is actually pretty impressive considering the pricing.
This echo is typically within the range of 200 ms – 700 ms, and it varies a bit. But, what happens when this delayed speech hits your ears?
You have a tendency to start stumbling over your words, and you more or less, just lose your train of thought. I’m thinking this may be due to the way your brain processes your words; since there’s an inherent “delay” that your mind creates, it somehow interferes with your speech processing center.
It’s a pretty funny thing to play with and show people the effects of. However it’s not foolproof; if you concentrate hard enough, and speak slowly you can overcome the effects of the jammer. It’s still amusing to see your friends think “oh, this’ll be easy!” and then proceed to have the speech capability of a 2-year-old.
The circuit itself is quite simple, too. Only three “active” components, the 5 volt regulator, the PT2399, which controls the delay, and the LM386 which amplifies the audio from the PT2399.