Wireless headset solution design and development

Wireless earphones, as the name suggests, are earphones in which the middle wire is replaced by radio waves, the transmitter is connected to the audio device, and the radio waves are transmitted to the receiver in the earphone through the transmitter to realize signal transmission. The wireless earphone consists of three parts: the first part is the transmitter, the second part is the receiver, and the third part is the earphone part. The function of the earphone part is mainly used to convert the electrical signal transmitted by the receiver into sound and then transmit it. into the human ear.

The biggest difference between wireless earphones and wired earphones is that there is no intermediate cable replacement, and there is no big difference in sound quality. Therefore, the development of wireless earphones is basically a process of following the continuous progress of communication technology. The development of wireless earphones has experienced several stages of evolution such as FM frequency modulation, infrared, 2.4G, and Bluetooth. Each generation of technology improves in terms of audio quality, signal transmission speed, transmission bandwidth, and cost of high-quality audio-visual equipment.

1. Technical classification of wireless earphone solutions

1. FM wireless headset

The full name of FM is Frequency Modulation, FM for short. FM is used to refer to general FM broadcasting (76-108MHz, 87.5-108MHz in my country and 76-90MHz in Japan). In fact, FM is also a modulation method, even in the range of 27-30MHz in the short wave range. Wireless earphones used FM technology at the earliest. The earphones are equipped with FM receiving circuits, and then the FM transmitter transmits audio signals to form signal transmission. The application of this principle also adds a radio function to this type of earphone. Due to the use of FM technology, the diffraction of the signal is strong, and the use distance can be as far as 70 meters. However, due to the highest sampling rate of 22KHZ in FM, its auditory performance is poor, and its confidentiality is not high and it is extremely susceptible to interference. It can only carry out one-way signal transmission, and the characteristics of low bandwidth also make it impossible to integrate wireless headsets. These shortcomings also make such headphones often positioned in the low-end market. Domestically produced FM wireless earphones can be seen everywhere in the market, and they are mainly used in foreign language listening training, foreign language testing and other fields.

2. Infrared wireless headset

The full name of infrared is infrared, which is an electromagnetic wave that can realize data transmission. In 1800, the British astronomer Herschel discovered infrared for the first time. Objects in nature, when the temperature is higher than the absolute temperature (-273 degrees Celsius), the surface will radiate infrared rays. Infrared is also a light wave, so it is rarely disturbed by the outside world except for strong light. This stable feature is widely used in early wireless transmission, such as infrared wireless mouse, infrared keyboard, mobile phone remote control and so on. Infrared transmission is a point-to-point transmission, which is generally suitable for low-cost, cross-platform, point-to-point high-speed data connection needs. In audio transmission, the biggest advantage of infrared wireless technology lies in the bandwidth, which can transmit the audio signal to the maximum capacity, and the sound quality is better.

But infrared rays also have many disadvantages. First, the point-to-point transmission mode limits the docking angle between the transmitting end and the receiving end. If the docking angle deviates greatly, the signal is likely to be unacceptable. In addition, the infrared transmission distance is not very long, and the general effective distance does not exceed 10m. The transmission power of infrared transmission is relatively high, which makes the battery replacement or charging of wireless earphones more frequent.

3. 2.4GHz wireless headset

2.4GHz is a working frequency band, and its frequency range is between 2.405GHz-2.485GHz. His frequency band belongs to the international free common frequency band, so working in the 2.4GHz frequency band has a larger range of use and anti-interference ability. Its biggest advantage lies in the data transmission rate. Using the P2P protocol, the theoretical transmission rate of 2.4GHz wireless technology can reach 2Mb/s, which exceeds the requirement of "CD-level sound quality" of 1.4Mb/s. In addition, it can basically meet the standard of lossless transmission, and its working mode is duplex mode transmission, which makes it have super anti-interference ability. 2.4GHz wireless technology is widely used in the low-end product market due to its low cost and superior performance.

The maturity of 2.4GHz wireless technology has also promoted the development of 2.4GHz wireless headsets. The core work of wireless earphones is to process audio signals, which are transmitted wirelessly between the audio source and the earphones. 2.4GHz high-speed data transmission capability and super anti-interference determine the excellent sound quality and excellent stability of this type of wireless headset. In addition, the 2.4GHz technology consumes less power and saves more power. With the popularization of the Internet, the market of 2.4GHz wireless earphones will have more potential, which is the general trend of earphone development in the future.

4. Bluetooth wireless headset

The name of Bluetooth (Bluetooth) comes from a Danish king, Harald Bluetooth King, who now takes the meaning of "unification", and the founder of this technology is Ericsson, and the technical standard was later set by the Bluetooth SIG. Bluetooth is also a wireless transmission protocol based on 2.4GHz technology, the difference is that the protocol used by Bluetooth is the IEEE802.15 protocol. In terms of anti-interference, Bluetooth technology has a unique solution. Bluetooth uses FM technology in particular, that is, the channel is divided into FM channels. When connecting, the radio receiver jumps from one channel to another according to certain rules. , due to different rules, it is difficult to be interfered by other signals. In addition, Bluetooth wireless technology does not require a fixed infrastructure and is very convenient to use. Therefore, it can be used in a wide range of applications, wirelessly connecting mobile phones, tablets, car stereos, headphones, MP3 players and many other devices. In addition, its biggest advantage is that Bluetooth products no longer need to install driver software. At present, this technology has developed quite maturely, and it will continue to develop in the direction of miniaturization, low power, low cost, safety, stability, ease of use and instant networking in the future.

Bluetooth technology can realize high-quality music transmission due to its low latency, low power consumption and high speed characteristics, and various Bluetooth headsets have emerged as the times require. The biggest advantage of Bluetooth headsets is that they can play high-fidelity music. At the same time, users can move freely in a large range without carrying audio equipment, which is very convenient, so the application space is huge.

5. Comparison of several wireless headset solutions

Each technology has its own advantages and disadvantages. We can see that FM wireless earphones are poor in anti-interference, but low in cost; infrared wireless earphones consume a lot of power and have limited use angles, but have little interference except for strong light. . The above two types of wireless earphones are representatives of early technologies. Due to the low technical threshold and generally poor sound quality, they can only appear in the low-end market. At present, the most widely used Bluetooth headset is the current TWS true wireless headset. Its high-speed transmission rate and excellent confidentiality allow users to connect the headset to other entertainment devices with Bluetooth functionality. Whether you're in the office, bedroom, living room, or driving, you can be instantly connected anytime.

2. The development trend of wireless earphones

With the continuous improvement of people's requirements for the quality of life, people have higher requirements for the comfort, material and functionality of earphones. From its birth to the present, earphones have been used as a simple tool for listening to songs, and now they have become a tool for people's daily communication, leisure and entertainment. The user experience brought by earphone series products is also getting higher and higher.

1. Technical development of wireless earphones

In terms of technology, the future technological development trend of wireless earphones will focus more on transmission distance, battery life, and connection diversification. In addition, the advantage of Bluetooth technology is that it is easy to use and has good stability. The future development of wireless headsets is inseparable from the Bluetooth attribute. This technology can be connected to other devices without a separate transmitter, which is more convenient to use.

There is also a new technology that completely subverts people's traditional perception of headphones, and it is bone conduction headphones. This kind of earphone only needs to put the earplug close to the front of the ear. Its principle is to transmit the sound to the human auditory system through the vibration of the earphone to the cheek. When we talk with our ears covered with our hands, we can hear our own voice, which is the principle of bone conduction. The advantage of this technology is that it can avoid the damage to the eardrum caused by listening to music for a long time, and you can also hear the sound from the earphones while hearing the sound of the surrounding environment. This new technology can make earphones more convenient to wear and more Safety. The disadvantage is that this technology consumes a lot of power, and its performance in terms of sound quality is average. I believe that with the improvement of technology, this kind of headset can be perfected day by day, bringing better user experience to consumers.

2. Functional development of wireless earphones

In terms of function, the current mainstream wireless headphones are nothing more than control keys such as play, pause, volume up, volume down, previous song and next song. With the development of the Internet, some products have been connected with mobile APPs to achieve more functions. This combination of software and hardware is also a major trend in future development. For the development of functions on headphones, is it better to have more functions? The answer is definitely not. Some functions must be based on the needs of users. By analyzing the needs of users, behaviors and usage environments, etc., we can find out the design pain points and design "easy-to-use, easy-to-use" wireless headset products. .

3. The appearance trend of wireless earphones

In terms of product shape, there is not much difference between wireless earphones and wired earphones, but the wireless earphones save the wire part so that there is more design space in the shape. If Apple mobile phones are "trendy toys", Korean clothes are "trendy clothes", and square dances are Chinese aunts' "trendy hip-hop dances", then having a wireless earphone with a unique shape is a great way for people to enjoy it at home, dormitory, shopping, shopping, etc. "Trendy accessories" for the office. Especially for young people, earphones have gradually become an expression of personality, taste, and fashion, and have even become an accessory that can be matched with different clothes. The design of earphones is becoming more and more important, and future wireless earphones will be diversified, lightweight, and portable. Diversification can get rid of the mainstream and attract more attention; lightweight design is convenient for travel and sports; portability can be convenient for storage when not in use. In the future, fashionable and personalized appearance design will become a bigger selling point of products under the trend of "homogenization" of technology.

3. Analysis of the sounding principle, structure and material of wireless earphones

The wireless headset is mainly composed of three parts: one is the source, the other is the receiver, and the third is the earphone part. Except that the cable is replaced by electric waves, the structure of the wireless earphone is basically the same as that of the wired earphone. The earphone part is mainly composed of four parts: a headband, a left and right sound unit, an earshell, and earmuffs or earplugs. The sounding principle of the earphone is similar to that of the loudspeaker of the sound box, which converts the electrical signal of the sound change into a sound signal. The earphone is also a kind of loudspeaker, which belongs to the electric loudspeaker. Headphones are functionally equivalent to a personal speaker, but because they are most "intimate" in contact with people's ears, they have higher requirements for use and wearing.

1. The sound unit of the earphone

The sounding principle of wireless earphones lies in its sounding unit, which is also the component with the highest technical content. In fact, it is the speaker end that finally emits sound. According to the principle of energy conversion, earphones can be divided into four types: moving coil type, moving iron type, electrostatic type and equimagnetic type.

The moving coil type is the most common, and its characteristics are: low cost, high efficiency, high durability, and can withstand high current input. At present, nearly 99% of the products on the market adopt this principle, and the consumer groups they face are mainly ordinary consumers who do not have high audio requirements. Its principle is that the loudspeaker emits magnetic force through a high-strength permanent magnet, so that the surrounding is covered with magnetic induction lines, and a winding coil is attached to the circular diaphragm and passes through the permanent magnet. When a current passes through, the magnetic force and the original magnetic field repel or attract each other, and vibration occurs.

The moving iron type also has a long history. It is characterized by its small size, which allows the earphones to penetrate deeper into the ear canal. Its working principle is that a connecting rod called "balanced armature" in the center of the permanent magnetic field drives the diaphragm to produce sound under the action of magnetic force. In terms of sound quality, the moving iron unit has a stronger graininess and excellent resolution. In order to make up for the shortcomings of the small unit area of the diaphragm and the insufficient frequency response range of the moving iron type, many products have been designed with multiple units.

The electrostatic type can be said to be the aristocrat among speakers, and it is completely designed for music enthusiasts. Exquisite shape, exquisite craftsmanship, perfect sound quality and expensive price are the common features of this series of headphones. Among them, Sennheiser and Orpheus are the most representative. Its principle is to directly plate or print the conductor coil on a thin plastic film, place it in a strong electrostatic electric field, and cut the electric field when the signal passes through the coil, driving the diaphragm to sound. In terms of sound quality, the electrostatic type has perfect resolution and high-frequency transparency, high fidelity, and the most important thing is that the diaphragm is very light, which can make the sound more delicate, the transient response is better, and the transmission speed is faster. quick. However, this technology does not perform well at low frequencies, and is prone to irreversible failures in high-humidity environments.

The equimagnetic principle is also known as the flat-panel principle, which is somewhat similar to a flat speaker. Its voice coil is planar, placed inside the diaphragm, and magnets are distributed on both sides of the diaphragm to vibrate in the magnetic field. The isomagnet also has a similar large vibration area and sound quality, but the diaphragm is not as thin as the electrostatic type. This type of earphone requires high power and high current, and due to its relatively large size, it is not suitable for long-term wearing.

2. Headphone headband

The function of the headband is to fix the left and right sounding units, we often call it a U-shaped bracket. According to the way of wearing, earphones have different forms, including head-mounted, ear-hook and in-ear. The U-shaped bracket we often refer to generally refers to head-worn earphones. Most in-ear and ear-hooks do not have a head beam structure. The headband plays an important supporting role. The structure of the headband and its connection with the sound unit directly determine the force of the earmuffs on the head, and also directly determine whether the earphones will be comfortable and firm when worn. Therefore, there will be rod structures on both sides of the headband, with built-in iron sheets and slides to adapt to different head sizes. There is also a headband design that can automatically fit the head, called adaptive headband, which is a two-layer layout of the headband, relying on the sliding structure as the connection, the user does not need to deliberately adjust the length of the head beam when wearing it, as the wearing process Automatically adjust the length according to the size of the human head, which is simple and effective.

3. Earmuffs

Earmuffs are parts that are in close contact with the head and the sound-generating unit. We sometimes call them earmuffs. Its function is not only to ensure comfortable wearing, but also to reduce noise and protect hearing. There are three styles of earmuffs for wireless earphones: the earmuffs that are pressed against the ears are called earmuffs; It can also be called earplug type, which can go deep into the ear canal.

For mid-to-high-end headphones, the earmuffs are very important, and the earmuffs are also an important part of the acoustic structure. For large earmuffs, the distance between the ear and the diaphragm can be separated to form a cavity between the earphone and the head, with a sealed gasket inside, and the material of the earmuffs can absorb mid-frequency and high-frequency. To a certain extent, it can also enhance the low frequency, and the sound directly acts on the ear gallery, which has a great impact on the sound quality.

Earmuffs are parts that are in direct contact with human ears, so softness and comfort should be fully considered in the material selection of earmuffs. For headphones, there are generally two types of earmuffs: circumaural and press-ear. The materials of earmuffs generally include sponge, flannelette, leather, and silicone. Sponge earmuffs are low in cost and highly breathable, but they are easily scratched; velvet earmuffs are good to wear, but they are not resistant to dirt; leather earmuffs have a good texture, high-end and stylish, but poor air permeability, and are more comfortable to wear in summer Poor; the silicone earmuffs are soft, cool and suitable for summer wear.

There are generally two types of earmuffs used in in-ear headphones, namely silicone and sponge. Silicone earmuffs can be single layer or multi-layer. Single-section silicone is the most common and common type. There are earmuff accessories of different sizes for easy replacement. Common sizes include S, M, L, SS, and LL. In terms of texture, there are also two types of soft and hard. The soft one is more comfortable to wear and will not cause too strong foreign body sensation in the ear canal, but the disadvantage is that the sound insulation performance is poor, and the hard silicone sacrifices the comfort, but it has better sound insulation. Effect. Among the single-section silicone earmuffs, there is also a special type, that is Sony's proprietary Columbia earmuffs, which use colored sleeves, earmuffs are made of soft silicone, and a foam silicon is filled between the sleeves and earmuffs. Quality cover, to make up for the defects of soft silicone in the sound insulation effect.

4. Ear shell

The ear shell is the shell that carries the sound unit. The earshells of wireless headsets generally have volume adjustment and switch control buttons for the earphones, and the buttons are usually raised above the surface of the earshells, which is convenient for users to perform blind operations. The inside of the ear shell of the wireless headset is generally the earmuff part. In addition, the microphones of wireless earphones are often placed on the ear shells, some are completely hidden inside, some are semi-hidden, the most common is the strip microphone on the traditional earphone, and some microphones are integrated into the remote control. located in the cable section. Our most intuitive visual perception of a headset comes from the design of the earshells. But the ear shell also has an important function, which is to act as the box of the speaker. According to the product structure, ear shells are divided into three categories: open type, semi-open type and closed type.

Compared with traditional wired earphones, wireless earphones add wireless communication devices inside the ear shell, such as decoding circuits, power supply systems, batteries, etc. If it is 2.4G technology, a transmitter also needs to be configured. For Bluetooth headsets, this component can be omitted, because the transmitter has been integrated in the audio source device.

Summarize

As a portable and compact audio output device, earphones are gradually integrated into modern life. In the market, there are various types of earphones, and the wearing methods are also varied, including earplugs, ear-mounted, in-ear, and head-mounted; in terms of structure and function, there are semi-open and closed. For sports people who listen to music, not all types of headphones are suitable for wearing.

During exercise, due to excessive movement, the earphones are often not easy to wear stably and are easy to fall off. During the exercise of traditional wired earphones, the cable is easy to rub and collide with the clothes, resulting in annoying noise. In addition, the swinging back and forth of the cable is not conducive to the athlete's body movements. When summer comes, a lot of sweat stains will also affect the wearing comfort of the earphones. With the development of the information industry and the application of wireless transmission technologies such as Bluetooth, wireless earphones have gradually become the new darling of the market. In recent years, in order to meet the requirements for earphones during sports, sports wireless earphones that are comfortable to wear, beautiful in appearance, compact and portable have gradually become popular in the market. As a kind of popular sports culture and entertainment consumption, sports wireless earphones will have a huge consumer market in the domestic market in the future.

The above are the details of the wireless headset solution introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have electronic function development needs for TWS earphones, you can trust us. We have rich experience in customized development of electronic products. We can evaluate the development cycle and IC price as soon as possible, and can also calculate PCBA quotations. We are a number of chip agents at home and abroad, including MCU, voice IC, Bluetooth IC and modules, wifi modules. Our development capabilities cover PCB design, single-chip microcomputer development, software custom development, APP custom development, WeChat official account development and other hardware and software design. It can also undertake the research and development of smart electronic products, the design of household appliances, the development of beauty equipment, the development of Internet of Things applications, the design of smart home solutions, the development of TWS solutions, the development of Bluetooth audio, the development of children's toys, and the development of electronic education products.