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Electronics Projects

       Project Prep

When’s the last time you stepped outside your door and really listened to all that noise out there? There are birds, traffic noises, maybe a cat slinking through the tall grass. Of course, some of these sounds you can pick up with your own two ears, but others aren’t so clear. A microphone that could help you pick up those softer sounds — whether made by your buddy whispering to you 100 feet away or birds in the trees — might come in handy. In this project, we show you how to put together a microphone and an IC to amplify noises that it picks up. Then you can put the whole circuit together with a parabolic (curved) metal dish that picks up sounds, just like how cupping your hand behind your ear helps you pick up sounds.

What a Dish! The Project Overview

A parabolic microphone kind of looks like a TV satellite dish. Instead of picking up electromagnetic broadcast waves, though, this kind of microphone picks up sound waves. Sound waves are simply vibrating molecules that deliver all kinds of sounds, like birds chirping and your neighbors’ latest argument. (Disclaimer: Of course, we’re NOT recommending that you use this project to eavesdrop on anybody!) You use the microphone, the curved dish, and headphones to gather and deliver the amplified sound to your ears.

You can see the finished parabolic microphone (and our own author, Earl, lurking behind it) in Figure 6-1.

figure 6-1

Here are the types of activities that you’ll be doing to create your own parabolic microphone. You will

1. Put together • An electronic circuit containing an electret microphone cartridge that can pick up faint sounds

• An IC that amplifies the sounds enough to power your headphones

2. Install the microphone in a parabolic dish that gathers sound like a giant ear.

We use a parabolic dish because the shape gathers sound and focuses it on a point — in this case, on the spot where we put the microphone cartridge. When you point the parabolic dish at a bird a hundred feet away, for example, the dish gathers sound only from the exact direction you point toward and focuses the sound on the microphone cartridge.

3. Add a handle made of pieces of plastic pipe so you can hold the dish up easily and aim it at the feathered or non-feathered friend of your choosing.