How to make a microphone out of a matchbox and a pencil


Reminds me of the scene in Cryptonomicon where Waterhouse makes a microphone mounted on a safe to crack it.

Hunh. I had seen that done with razor blades and pencil-leads, but never with the leads-alone. Approximately-ten-year-old-me was fascinated by how that worked. Probably more so than by the no-battery-required crystal radio, which he* still considers to be more akin to magic.

* non-ten-year-old me

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Here’s a viddy about making that Cryptonomicon mic:

So, a viral ad for headphones. BTW, this is essentially how carbon granule microphones worked in old telephone sets. I used to have to test them - there was a spec on how to move them prior to testing to shake up the granules to make them work correctly.


Many things will modulate voltage or current with applied mechanical forces. It can be quite a bitch if you need to eliminate those effects, whether in precision instrumentation or because of security.

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