Interpret the “password” behind the application of active noise reduction (ANC) technology “breaking the circle”
Since Apple launched AirPods in 2016, the emerging market of split true wireless (TWS) headsets has been gradually resolved with the ultimate convenience brought to consumers, as well as the pain points of transmission, battery life, and price, which has triggered a new round of growth. Volume market.
According to the “Global Bluetooth Headset Sales and Revenue Forecast 2001-2024” report released by the world-renowned research organization Strategy Analytics, the sales of TWS Bluetooth headsets increased by 200% in 2019, and the market size of TWS headsets is expected to reach 100 billion by 2024 Dollar.
The ANC (Active Noise Cancellation) function is becoming the standard configuration of TWS headphones due to its practicality. It is expected that by 2023, more than half of TWS headphones will have ANC function. Therefore, how to add excellent noise reduction functions to small and portable TWS headsets is becoming a key focus of the product design of headset manufacturers.
Crack the secret of quietness, this noise reduction technology is becoming mainstream
In fact, for TWS headsets, the most basic needs of users are portability and long battery life. Above this, users’ main needs are clear and clean listening experience.
Today, when environmental noise is flooding our various life scenes all the time, this requirement is not easy to achieve, and the demand for noise reduction is getting higher and higher.
Although passive noise reduction by enclosing the ears to form a closed space or using sound-insulating materials such as silicone earplugs to block external noise can effectively suppress high-frequency noise, it cannot do anything about low-frequency noise, and it depends on low-frequency noise reduction.
Active noise reduction
For active noise reduction. The active noise reduction function is to generate an inverted sound wave equal to the external noise through the hardware noise reduction system, neutralize the noise, and achieve the effect of noise reduction.
Active noise reduction has analog and digital noise processing circuits. Although analog circuits have basically zero delay and digital circuits have delays, analog active noise reduction circuits have many components, large PCB sizes, and high precision requirements.
Therefore, digital noise reduction is the current mainstream. In addition, in terms of flexibility, analog active noise reduction methods are limited, mainly focusing on volume adjustment, while digital active noise reduction can optimize the noise reduction effect by adjusting gain, EQ coefficient, and updating firmware.
The consistency of the analog active noise reduction circuit is very poor, requiring multiple and repeated adjustments and calibrations on the hardware; the digital active noise reduction has good consistency, and there are corresponding adjustment tools and software to easily achieve calibration.
Finally, the BOM cost of analog active noise reduction seems to be low, but the defect rate and rework rate are high, and the overall mass production cost is actually higher than that of digital circuits.
Therefore, analog active noise reduction is becoming a yellow flower of tomorrow, and digital active noise reduction has become the mainstream of the market.
In terms of implementation, active noise reduction can be divided into three types: feedforward , Feedback, and a hybrid of the two (Hybrid).
The feed-forward active noise reduction earphones are generally located outside, collect the noise and send it to the DSP for processing, and then output the inverted sound wave for noise reduction.
The microphone of the feedback type active noise reduction headset is located inside the cavity, and the noise collected and sent to the DSP is basically the same as what the ear hears, and can be directly reversed.
The hybrid active noise reduction combining the two methods can achieve faster and better noise reduction effects.
“At present, although the cost of hybrid active noise reduction is relatively higher, as the cost of chips and microphones decreases, this method that can bring a better listening experience will surely become the first choice of manufacturers.
Chip + software modular solution to solve the core pain points of headset ANC
Therefore, the focus of TWS earphone noise reduction is to accurately collect noise, quickly process and output the canceled inverted sound wave, and also have the lowest possible power consumption to achieve long battery life. The three core parts of active noise reduction are ADC, DSP and DAC.
As ADI, which has always been leading the way with high-performance analog technology and digital signal processing technology, it naturally obtains first-mover advantage in ADC, DAC and DSP, and it handles well.
In addition to the most sensitive microphone signal in the ANC system, it has demonstrated strong signal processing capabilities while ensuring ultra-low power consumption, and at the same time demonstrated its profound skill in small chip packaging and low power consumption.
The “headphone ring” is popular, and the application of ANC technology in more scenarios is discussed
In fact, not only is it thriving in the application of TWS headphones, ANC technology is also gradually “out of the circle”, acting on the active noise reduction of the open sound field in three-dimensional space.
This requires not only excellent active noise reduction algorithms, but also a profound acoustic theory background, modeling, analysis, simulation, and noise reduction of the three-dimensional sound field in order to achieve active noise reduction in specific areas under the premise of non-wearing, and thus greatly expand Application scope.
At present, the application of active noise reduction technology in three-dimensional space is relatively mature in the car cockpit.
Generally speaking, in addition to the noise mainly from the engine when the vehicle is driving, there are also tire noise, wind noise and noise from the external environment. Similar noise collection and noise spectrum analysis are used to eliminate noise. purpose.
Not long ago, ADI and Hyundai Motor Co., Ltd. cooperated to launch the industry’s first all-digital road noise reduction system.
Its core part uses ADI’s A²B audio bus technology to solve the key challenge of electronic acquisition signal transmission delay;
with DSP algorithms to ensure the interior independence of the sound zone in different positions and the realization of echo cancellation, and the ANC active noise reduction with the power amplifier of the microphone.
In addition, today with a comprehensive upgrade of consumption, there is a strong demand for noise reduction technology in the home appliance field, but the application and layout of the application is still a blue ocean.
As the main focus of the household market, for example, the various noises from mixers, vacuum cleaners, and toasters make many consumers worry about it.
At CES2020 at the beginning of this year, ADI demonstrated the active noise reduction function of household appliances (coffee machines) based on the ADAU1452 audio processor, which can achieve a 10dB noise reduction effect.
This type of solution can also be applied to household appliances that produce louder noises, such as soymilk machines, range hoods, etc., so that uncomfortable noises disappear from the home environment.
In fact, ANC-based innovation is far more than that. The ubiquitous noise and people’s pursuit of a comfortable environment make ANC technology innovation and application space huge.
ANC technology can also be applied to hearing aids.
Through a similar selective permeability, mode to receive specific sounds and combined with bone conduction related technologies.
Adding sound collection and amplification equipment similar to ANC to people with hearing impairments can help Hearing sounds and to improve the perception of external sounds are also a future application development trend.
The industry generally believes that 2020 will be the most critical year for competition in the TWS headset market. Mobile phone manufacturers continue to enter TWS Bluetooth headsets.
Traditional headset brands are even more powerful. New headset brands are advancing rapidly, which will surely drive the differentiation of the TWS market.
The price of mid-to-high-end products with lower cost and higher performance will drop due to the scale effect, allowing more people to enjoy the charm and fun of technology.