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Parabolic Microphone

This dollar store DIY spy mic lets you listen from afar.

Parabolic Microphone

This is a ridiculously easy way to build a parabolic microphone using dollar store items. You’ll attract lots of attention walking around in public with this rig. I usually welcome the inquiries, and let people listen to what I’m doing. Kids especially love it.

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Steps

Step #1: Make the dish

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Parabolic Microphone

Use wire cutters to snip away the 4 plastic holders that connect the hat’s umbrella to its headband.

Step #2:

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Parabolic Microphone

Slice the top of the plastic knob off the top of the umbrella, and clean up the hole with a knife or reamer.

Step #3:

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Parabolic Microphone

Cover 1 gore of the umbrella near the center with a trapezoidal piece of the gaffer’s tape. Cut a small X-shaped incision through the tape and umbrella; this will be the reinforced hole that the microphone wire will pass through.

Step #4: Attach the handle

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Parabolic Microphone

Remove the paint roller’s plastic caps and wire frame. Push the shaft through the hole in the top of the umbrella, so that it protrudes 6" underneath. Leave ½" of clearance between the outer surface of the umbrella and the bend of the handle.

Step #5:

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Just above the umbrella’s top knob, wrap a length of tape around the shaft and ring it with a cable tie pulled tight. Wrap the the shaft with more tape, to provide a gripping surface for the microphone.

Step #6: Install the microphone

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Parabolic Microphone

Clip the mic to the shaft and thread the cable through the X hole. Secure the cable with cable ties.

Step #7:

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  • You want to place the microphone at the focal point of the reflector, but realize that this is a plastic umbrella, not a perfect parabola. So this “point” will be more of a semifocal blur. Here are 3 ways to position the mic, in decreasing order of complexity:
  • Point a laser at different points on the inside of the umbrella from a distance of about 20 feet directly in front of the unit. Mark where it reflects onto the shaft to find the general region of focus.
  • Plug the mic into a recording device, put on some headphones, and point it toward a ticking clock some distance away. Move the microphone along the shaft until you get the loudest sound.
  • Just take my word for it, and position the mic about 3" from the inside surface of the umbrella.

Step #8: Take it for a test ride

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Parabolic Microphone
  • Plug your new parabolic mic into a recorder. Use headphones to monitor your work. Then point it at something interesting. You’re in for a pleasant surprise!
  • Now try recording the same sound without the parabolic setup — forget it.
  • Hear field recordings of a squirrel and a cardinal made with the Dollar Store Parabolic Mic at http://makezine.com/14/diyspy_mic.

Conclusion

This project originally appeared in MAKE Volume 14.

Related Posts on Make: Online:

Weekend Project: Parabolic Microphone

http://blog.makezine.com/archive/2008/06...

Build a spy bug with off the shelf parts

http://blog.makezine.com/archive/2008/10...


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