Electronic Enthusiasts Network reported (text / Li Cheng) With the popularization of active noise reduction, spatial audio, 360-degree surround sound, and the continuous drop in chip costs, the TWS headset market has been thoroughly detonated, and the market penetration rate has been significantly improved. , and major consumer giants have also entered the TWS headset market one after another, constantly iterating and updating, hoping to get a share of the TWS outbreak.
With the advancement of technology, TWS headphones are no longer mediocre. The addition of various voice assistants and spatial noise reduction functions has led to a surge in the number of electronic components used, and the energy consumption of equipment has also increased. In addition, the small space inside the headphones also limits TWS. The development of multifunctional headphones. Therefore, in order to ensure more durable battery life and the development of multi-functional headphones, terminal manufacturers have put forward higher hardware requirements to upstream core component manufacturers.
In TWS earphones, speakers and batteries occupy most of the space. With the increase of functions, the internal space of TWS earphones is further tightened. Therefore, under the premise of ensuring battery life, optimizing the size and power consumption of speakers has become a Optimal solution. In order to meet the development needs of the TWS earphone market, many manufacturers have successively released MEMS speakers with smaller size, low power consumption, and strong scalability to replace the traditional coil speakers to meet the application needs of the market.
MEMS speakers for earphones, smart glasses
Recently, xMEMS Labs introduced Tomales, a highly scalable single-chip MEMS piezoelectric driver tweeter. The MEMS speaker technology of xMEMS is mainly based on the inverse piezoelectric effect of piezoelectric MEMS materials. Its working principle is to apply a voltage to the piezoelectric MEMS. When the piezoelectric MEMS receives an electrical signal, the silicon film will transmit the electrical energy. Converted into mechanical energy, do expansion, contraction movement and generate sound waves. Piezoelectric MEMS of xMEMS Compared with traditional loudspeakers, the mechanical motion of xMEMS silicon membrane is larger, which can produce louder audio effects.
Image source: xMEMS
Tomales is a single-chip MEMS tweeter that can realize multiple application scenarios. According to xMEMS, Tomales adopts a single-chip architecture. The advantage of this structure is that the driver and the diaphragm are integrated on the same silicon chip, which is highly integrated. It helps to improve the consistency of the response frequency of each device, improve the ANC bandwidth of non-steady-state noise, and reduce the matching and calibration time in the product production process. The use of this architecture removes the process of restoring the traditional speaker spring and suspension, which not only greatly restores the sound quality of the original audio, but also improves the user experience.
At the same time, this MEMS speaker also adopts IP58 dust/waterproof design and 6.05 x 8.4 x 1.15mm LGA package, which further reduces the difficulty of speaker layout and the space ratio between the device and the speaker. The extremely small product volume is very suitable for It is used in devices with small internal space and designated audio orientation, such as headsets, smart glasses, and AR/VR.
In terms of product performance, according to xMEMS, Tomales adopts its own unique second-generation M2 speaker unit architecture, and optimizes the architecture to achieve the effect of small speaker sound pressure. The decibel test experiment was carried out at a distance of 3 cm from Tomales. , when the operating frequency is 2kHz, the decibel test result is 75dB. When the operating frequency is 4kHz, the decibel test result is 90dB. When the operating frequency is 10kHz, the decibel test result is 108dB. The sound field effects produced by different operating frequencies can meet the needs of general product applications. The new product is still in the sample stage and is expected to be mass-produced in 2022, but the company's Montara MEMS speaker has already been mass-produced and has been used for the first time in Hyunin's flagship TR-X TWS in-ear headphones.
Nanoelectrostatically driven MEMS speaker
According to foreign media reports, the Fraunhofer Institute for Optical Microsystems successfully developed a MEMS micro-speaker using nano-electrostatic drive technology in October this year. It is reported that the speaker is made of 100% silicon material. The loudspeaker's sound-emitting diaphragm is also replaced by a curved ribbon made of silicon wafer sheets, and the cost advantage of this MEMS microspeaker can be seen only from the raw materials used.
The loudspeaker mainly uses nano-electrostatic driving technology to generate sound in the silicon chip. When the chip is etched, a very small electrode gap is generated, and the high electrostatic force generated by the electrode gap is used to drive the bending belt to produce bending motion in the chamber. . When the bending belt in the chamber is doing a bending motion, the vibrations generated will push the air out of the chamber and produce a sound. The loudspeaker can be used in only 10mm2up to 120dB of sound pressure over the effective chip area (displacement air volume of about 0.5 mm3ok).
At the same time, the curved band of the speaker can also be arranged and optimized according to the frequency range of different applications. If it is desired to increase the sound pressure level of the loudspeaker, it can also be achieved by increasing the thickness of the wafer during the wafer production stage.
According to reports, this MEMS micro-speaker can achieve a large audio frequency range from 20Hz to 20kHz. It has the characteristics of small size, light weight, low power consumption and strong expandability, which can meet the application of miniaturized products such as TWS headphones and hearing aids.
With the increase in the functions of wearable devices such as TWS, AR/VR, and smart glasses, MEMS speakers with smaller size, power consumption and wider frequency range have become the most advantageous solutions. The successful research and development of 100% silicon MEMS speakers will help terminal manufacturers to control the cost of products and improve the market competitiveness of products.