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.
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.
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.