Related Devices
There is also another common design of piezoelectric transducer. This is made of a disk of brass that is coated with barium titanate ceramic. When electricity is connected to it, the ceramic bends the brass disk, causing sound vibrations. These provide much greater sound output than crystal earpieces, but have insufficient bandwidth for earpiece use. They are widely used as resonant bleepers.
Where cost is the main concern, the most popular type of minimum cost earpiece and microphone today is moving iron. These offer better sound quality and lower price than crystal, and are more robust.
Read more about this topic: Crystal Earpiece
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