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Un piezo pour produire du son
Par Stéphane
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On peut produire du son avec un piezo, grâce à des fréquences rapides.

Piezo buzzer's can be bought at electronics and consumer electronics stores. I bought the one below at Radio Shack. The packaging on it says:

Part number: 2730060
Operating voltage: 4-28VDC
Current consumption: 5mA (max.) at 12VDCVCC
Sound level: 86dB at 11 7/8" (30cm) 12VDC/VCC
Resonant frequency: 3500 +/-500 Hz

Normally you apply a DC voltage to it and it produces a loud, annoying buzzing sound. In the photo on the right you can see that I cut off a part of a pen and hot glued it over the hole in the piezo buzzer so that it can better direct the sound into my ear when used as a crystal earphone.

Piezo buzzer and the packaging.
Piezo buzzer bought from Radio Shack and the packaging it came in.
Piezo buzzer modified for crystal earphone.
Piezo buzzer modified to make it work as a crystal earphone.

Piezo speakers from microwave ovens

If your microwave oven makes a beeping sound when food is ready then it may have a piezo speaker inside. If the microwave oven has a dial-type of timer that makes a bell ringing sound then it doesn't have a piezo speaker.

In the rightmost photo below you can see that I cut a short length of tubing, a part of a pen, and hot glued it over the hole in the speaker. This is to better direct the sound into my ear.

Piezo speaker in the microwave oven.
The location of the piezo speaker in the microwave oven.
The piezo speaker by itself.
The piezo speaker having been removed from the microwave oven for use as a crystal earpiece/earphone.
Piezo speaker modified for crystal earphone.
The piezo speaker with tube added to better function as a crystal earpiece/earphone.

In my case the piezo speaker from the microwave oven had its back exposed. My fear was that some of the sound would escape in this direction when really I wanted it all to go into my ear through the tube glued to the other side. So, as the photos below show, I hot glued a piece of hard plastic over the back.

Exposed crystal and DIY plastic cover.
The exposed piezoelectric crystal from the microwave oven's piezo speaker and the homemade plastic cover.
The cover hot glued in place.
A plastic cover hot glued onto the back of the microwave oven's piezo speaker so that it would better function as a crystal earphone and better direct the sound into my ear.

Video showing how to make a crystal earpiece using a microwave oven speaker

The following is a very complete video about how to make a crystal earphone from a piezo speaker, in this case from a microwave oven. But even if you got the piezo crystal from any of the above sources, this video will still be useful.