A piezoelectric speaker, also known as a piezo speaker, operates based on the piezoelectric effect, which is the ability of certain materials to generate an electric charge in response to applied mechanical stress, or conversely, to deform when subjected to an electric field. The working principle of a piezoelectric speaker involves this unique property of piezoelectric materials.
Here's a step-by-step explanation of how a piezoelectric speaker works:
Piezoelectric material: The speaker is built using a piezoelectric material, which is usually a crystal or a ceramic material like quartz, Rochelle salt, or lead zirconate titanate (PZT). These materials possess a crystalline structure that exhibits the piezoelectric effect.
Sandwich construction: The piezoelectric material is sandwiched between two electrodes (usually metal plates or foils) to form a piezoelectric element. When the electrodes are connected to an external circuit, they act as positive and negative terminals.
Electrical input: When an alternating electrical signal, typically an audio waveform, is applied to the electrodes, it creates an electric field across the piezoelectric material. This alternating electric field causes the material to rapidly expand and contract, vibrating at the same frequency as the electrical signal.
Mechanical vibrations: The rapid expansion and contraction of the piezoelectric material result in mechanical vibrations being generated. These vibrations travel through the material and are transferred to the surrounding medium, which is usually air in the case of most speakers.
Sound production: The mechanical vibrations in the air produce sound waves. The frequency of the sound waves corresponds to the frequency of the electrical signal applied to the piezoelectric material. As the electrical signal varies, the mechanical vibrations and, consequently, the sound produced also change.
Sound amplification: Piezoelectric speakers are not as efficient at converting electrical energy into sound as traditional magnetic speakers. As a result, they are often used for applications requiring lower power and sound output levels, such as small electronic devices, musical greeting cards, or toys.
Reverse operation: Piezoelectric materials can also operate in reverse. When subjected to an external mechanical force or pressure, they generate an electrical charge across the electrodes. This property is exploited in devices like piezoelectric microphones and certain types of sensors.
In summary, the working principle of a piezoelectric speaker relies on the ability of piezoelectric materials to convert electrical energy into mechanical vibrations, which then produce sound waves in the surrounding medium.