Piezoelectric Ceramics: From High-Frequency Compensation to Smart Tactile Feedback, Reshaping Audio and Interaction

Piezoelectric ceramics are polycrystalline materials formed through the high-temperature sintering of oxides and solid-phase reactions. After being polarized under high DC voltage, they exhibit unique piezoelectric properties. This material enables bidirectional conversion between mechanical energy and electrical energy. The piezoelectric effect comprises two aspects: the "positive piezoelectric effect," where applying physical pressure generates an electric charge within the material, converting mechanical energy into electrical energy; and the "reverse piezoelectric effect," where applying an electric field causes the material to deform, converting electrical energy into mechanical energy. These characteristics make piezoelectric ceramics particularly suitable for use as sound-generating elements.

The piezoelectric effect can generate an electric charge when physical pressure is applied or convert applied electrical energy into mechanical energy. (Image source: BeStar Technologies, Inc.)

In earphones, a piezoelectric ceramic driver utilizes alternating voltage to vibrate an attached underlying metal substrate, producing sound. This method offers high energy conversion efficiency and extremely fast response speed. Piezoelectric ceramics are exceptionally hard, second only to diamond. This property allows them, when used as a diaphragm material, to reproduce delicate and smooth string instrument tones with outstanding listening endurance.

Breakthrough Advantages of Dynamic Driver + Piezoelectric Ceramic Earphones

The innovative application of piezoelectric ceramic units in earphones effectively compensates for the shortcomings of traditional dynamic drivers in high-frequency response. The multi-layer piezoelectric ceramic series developed by BeStar Technologies, Inc. is specifically designed as a high-frequency compensation unit for earphones. It features a compact size, simple structure, and low driving voltage.

Compared to traditional dynamic drivers, piezoelectric ceramic units hold a significant advantage in high-frequency performance. While typical TWS earphones often claim a frequency range of 20 Hz to 20 kHz, dynamic drivers usually exhibit significant attenuation around 10 kHz. In contrast, piezoelectric ceramic units can maintain an attenuation of only 15 dB within 30 kHz and 30 dB within 40 kHz. This performance surpasses that of balanced armature drivers. Furthermore, compared to balanced armature drivers, the combination of dynamic and piezoelectric ceramic drivers does not require a complex crossover network, reducing audio signal loss during conversion, resulting in a more natural sound transition. This approach also helps reduce size and save costs.

Practical products, such as the HONOR Earbuds 3 Pro, which feature a coaxial dual-driver design combining a dynamic driver with a ceramic high-frequency unit, demonstrate the feasibility of this combination.

The HONOR Earbuds 3 Pro feature a coaxial dual-driver combining a dynamic driver with a ceramic high-frequency tweeter. (Image source: HONOR)

The Broad Potential of Piezoelectric Ceramics

The application of piezoelectric ceramic technology extends well beyond the realm of earphones. In recent years, this technology has shown great potential in areas such as automotive smart surfaces and haptic feedback. Ultra-thin piezoelectric ceramic sheets can be precisely integrated into vehicle interiors, capable of accurately recognizing press intensity while providing clear user feedback through micro-vibrations. The response speed of this technology is extremely fast, with the entire feedback process completed within milliseconds, offering users a seamless "press-and-response" interactive experience. These cross-industry applications demonstrate that piezoelectric ceramic technology is becoming a vital bridge connecting the digital world with physical experiences.

From piezoelectric gyroscopes in aerospace to ultrasonic diagnostics in healthcare, and from electronic lighters to earphones, piezoelectric ceramics have permeated numerous fields, becoming an indispensable multi-talented material in the information age.

With advancements in multimedia technology and increasing demands for sound quality, the application prospects of piezoelectric ceramic technology in the audio field are broad. Compared to traditional dynamic and balanced armature drivers, piezoelectric ceramics offer multiple advantages, including fast response, low energy consumption, and small size.

Piezoelectric ceramic drivers are directly driven, resulting in minimal energy loss, whereas dynamic and balanced armature drivers require converting electrical energy into mechanical energy through a magnetic field, a process involving greater energy loss. This positions piezoelectric ceramic technology advantageously for future technologies pursuing high efficiency and energy savings.

Summary

As piezoelectric ceramic technology continues to improve, we will see its applications in more devices. The integration of tactile and auditory feedback is set to become a crucial direction for the development of human-computer interaction.

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