- Structure of piezoelectric diaphragm -
Piezoelectric sound components necessary have piezoelectric diaphragms.
This is a simple structure which a piezoelectric ceramic is adhered to a metal plate of brass or nickel-alloy.
- Mechanism of producing sound for piezo diaphragms -
When a voltage is applied across the piezoelectric ceramics, it stretches in its plane. When a voltage is applied to piezoelectric diaphragm, as the metal plate does not stretch, it bends as shown in Fig (a). When the polarity of the applied voltage is reversed, the piezoelectric ceramics shrinks and the metal plate bends toward the opposite side as shown in Fig (b).
When the direction of applied voltage changes alternately, the state of Fig (a) and Fig (b) is repeated as shown in Fig. (c), producing sound waves in the air.
- Function of a case -
You can get higher sound by using the resonance effect when a product is case type.
1. The peak of sound pressure level of diaphragm
2. The peak of sound pressure level of amplified in a case
3. 10 to 20 dB higher sound pressure level by resonance effect
By designing fosc and fcav close each other, you will get 10 to 20 dB higher sound pressure level compared to non-cased diaphragm.
|Frequency in which a diaphragm resonate most efficiently.
|Frequency that sounds resonates through the case.
Fcav changes by dimensions of the case and the sound emitting hole.