Video: Piezoelectric microphone

In 1880, Jacques and Pierre Curie discovered a new property of certain crystals, which they named « piezoelectricity ».

These materials undergo deformation when a voltage is applied to them.

The two scientists also noted that the effect was reversible.

The same crystal undergoes electrical polarization when it is submitted to a deformation.

The word “piezo”, incidentally, comes from the Greek “piezein”, which means “compressor”.

It is this second property that is exploited in the piezoelectric microphone.

The sound wave makes one of the faces of the crystal vibrate, and one receives, at the poles of the two electrodes, a small voltage, proportional  to the deformation in the crystal.

This microphone technology  delivers a signal of lesser quality than dynamic and electrostatic  technologies.

But it turns out to be the best technology under certain extreme conditions:

To detect high frequency sounds, like ultrasound

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Or to listen in an aquatic medium with a hydrophone.