From TWS headphones to coffee machines, interpreting the "code" behind the "breakthrough" of active noise reduction (ANC) technology applications

Latest update time：2020-06-24

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Since Apple launched AirPods in 2016, the emerging category of split true wireless (TWS) headphones has triggered a new round of incremental market by bringing extreme convenience to consumers and gradually solving pain points such as transmission, battery life, and price. According to the research report "Global Bluetooth Headset Sales and Revenue Forecast 2001-2024" released by Strategy Analytics, a world-renowned research institution, TWS Bluetooth headset sales increased by 200% in 2019, and the market size of TWS headphones is expected to reach US$100 billion by 2024. Sophie Mao, consumer product marketing manager of ADI China, also said at a recent event that domestic TWS headphones are still in the extensive growth stage, and players at all levels will fully enter this market.

Sophie Mao, Consumer Product Marketing Manager, ADI China

The ANC (active noise reduction) function is becoming a standard feature of TWS headphones due to its practicality. It is expected that more than half of TWS headphones will have ANC function by 2023. Therefore, how to add excellent noise reduction function to compact and portable TWS headphones is becoming a key focus of product design for headphone manufacturers. As a world-leading supplier of data conversion and signal processing technology widely recognized by the industry, ADI provides a dedicated ANC SoC solution with unique advantages in the industry, and has been widely used in the flagship products of leading domestic and foreign audio manufacturers such as Bose, Bowers & Wilkins, and Edifier, and has attracted widespread attention.

▼Watch the video to learn more about ANC application scenarios▼

</p> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> </span> </p> <div data-id="98604" data-tools="135编辑器"> <div style="margin: 10px auto;text-align: center;"> <div style="display: inline-block;"> <div style="color: rgb(12, 167, 210);display: flex;justify-content: center;align-items: center;padding-right: 3px;padding-left: 3px;margin-right: auto;margin-bottom: -2px;margin-left: auto;"> <div data-brushtype="text" style="letter-spacing: 2px;font-size: 16px;font-weight: bold;"> <span style="font-size: 14px;"> Unlocking the secret of quietness: This noise-cancelling technology is going mainstream </span> </div> <div style="width: 30px;margin-left: 5px;"> <div style="width: 30px;"> </div> </div> </div> <div style="height: 1px;background-color: rgb(12, 167, 210);flex: 1 1 0%;margin-right: 40px;color: rgb(255, 255, 255);overflow: hidden;"> <br/> </div> <div style="height: 1px;background-color: rgb(12, 167, 210);flex: 1 1 0%;margin-top: 2px;color: rgb(255, 255, 255);overflow: hidden;"> <br/> </div> </div> </div> </div> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> In fact, for TWS headphones, the most basic needs of users are portability and long battery life. Above this, the main demand of users is a clear and clean listening experience. </span> <span style="font-size: 14px;"> In today's world where environmental noise is everywhere in our lives, this requirement is not easy to achieve, and the demand for noise reduction is getting higher and higher. </span> <span style="font-size: 14px;"> Although passive noise reduction by surrounding the ears to form a closed space, or using sound insulation materials such as silicone earplugs to block external noise can effectively suppress high-frequency noise, it is powerless against low-frequency noise, and low-frequency noise reduction depends on active noise reduction. </span> <span style="font-size: 14px;"> The active noise reduction function is to generate an anti-phase sound wave equal to the external noise through the hardware noise reduction system, neutralize the noise, and thus achieve the effect of noise reduction. </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> According to Sophie Mao, active noise reduction has two types of noise processing circuits: analog and digital. Although analog circuits have basically zero delay and digital circuits have delay, analog active noise reduction circuits are composed of many components, large PCB size, and high precision requirements, so digital noise reduction is the current mainstream. In addition, in terms of flexibility, analog active noise reduction methods are limited, mainly focusing on adjusting the volume, while digital active noise reduction can optimize the noise reduction effect by adjusting gain, EQ coefficient, updating firmware, etc. The consistency of analog active noise reduction circuits is very poor, and it requires multiple and repeated adjustments and calibrations on the hardware; 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 defective 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 has gradually become a thing of the past, and digital active noise reduction has become the mainstream of the market. </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <p style="line-height: 1.75em;text-align: center;"> </p> <p style="text-align: center;"> <span style="color: rgb(127, 127, 127);font-size: 12px;"> Analog noise reduction processing circuit vs digital noise reduction processing circuit </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> In terms of implementation, active noise reduction can be divided into three types: feedforward, feedback, and hybrid. Feedforward active noise reduction headphones are generally located outside, collect noise and send it to DSP for processing, and then output inverted sound waves for noise reduction. The microphone of feedback active noise reduction headphones is located inside the cavity. The noise collected and sent to DSP is basically the same as what the ear hears, and can be directly processed in reverse. The hybrid active noise reduction that combines 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." Sophie Mao emphasized. ADI's ADAU1787 SoC solution provides 4-channel ADC input interface and 4-channel digital microphone input, which is suitable for hybrid noise reduction headphones. </span> </p> <p style="line-height: 1.75em;text-align: center;"> <span style="font-size: 14px;"> </span> </p> <p style="line-height: 1.75em;text-align: center;"> <span style="color: rgb(127, 127, 127);font-size: 12px;"> The ANC (Active Noise Cancellation) chip uses a built-in microphone to monitor both the noise generated by external sources and the sound played by the headphone speakers. </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <div data-id="98604" data-tools="135编辑器"> <div style="margin: 10px auto;text-align: center;"> <div style="display: inline-block;"> <div style="color: rgb(12, 167, 210);display: flex;justify-content: center;align-items: center;padding-right: 3px;padding-left: 3px;margin-right: auto;margin-bottom: -2px;margin-left: auto;"> <div data-brushtype="text" style="letter-spacing: 2px;font-size: 16px;font-weight: bold;"> <span style="font-size: 14px;"> Chip + software modularization solves the core pain points of headphone ANC </span> </div> <div style="width: 30px;margin-left: 5px;"> <div style="width: 30px;"> </div> </div> </div> <div style="height: 1px;background-color: rgb(12, 167, 210);flex: 1 1 0%;margin-right: 40px;color: rgb(255, 255, 255);overflow: hidden;"> <br/> </div> <div style="height: 1px;background-color: rgb(12, 167, 210);flex: 1 1 0%;margin-top: 2px;color: rgb(255, 255, 255);overflow: hidden;"> <br/> </div> </div> </div> </div> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> Therefore, the key to noise reduction in TWS headphones is to accurately collect noise, quickly process it, and then output the inverse sound waves that cancel it out, while also keeping power consumption as low as possible to achieve long battery life. The </span> <span style="font-size: 14px;"> three core parts of active noise reduction are ADC, DSP, and DAC. As ADI has always been a leader in high-performance analog technology and digital signal processing technology, it naturally has a first-mover advantage in ADC, DAC, and DSP. It has delicately processed the most sensitive microphone signals in the ANC system, demonstrated powerful signal processing capabilities while ensuring ultra-low power consumption, and demonstrated its profound skills in small chip packaging and low power consumption. </span> <span style="font-size: 14px;"> </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> "ADI has a series of dedicated noise reduction solutions, such as the ADAU1787 ANC SoC solution, which provides 4 ADC input interfaces and 4 digital microphone inputs, and these inputs are parallel inputs, so the ADAU1787 can be used in hybrid noise reduction headphones with a single chip. At the same time, the ADAU1787 has a unique dual-core design, with the FastDSP core performing active noise reduction filter processing and the SigmaDSP core performing EQ post-processing to compensate for the low-frequency part of the music lost after noise reduction processing." Sophie Mao added, "The ADAU1787 2.3*2.8 mm BGA package consumes only about 6-7 mW at 1.8 V power supply, which is very suitable for TWS headphones with more stringent requirements on power consumption and chip size." </span> </p> <p style="line-height: 1.75em;text-align: center;"> <span style="font-size: 14px;"> </span> </p> <p style="line-height: 1.75em;text-align: center;"> <span style="color: rgb(127, 127, 127);font-size: 12px;"> ADAU1787 Simplified Functional Block Diagram </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> More and more manufacturers are joining the hot TWS market, which also brings concerns about product homogeneity in the industry. ADAU1787 modular technology also enables customers to create some differentiated features, such as allowing certain sounds to be played, eliminating other sounds, or automatically adjusting to certain parameters and responding to the environment, including voice enhancement, noise reduction, echo cancellation, level control, sound feedback suppression, microphone arrays, and active noise/vibration control. In addition, there are more thoughtful details hidden in the ADI chip, such as PID proportional integral differential control logic in the field of automatic control. It can predict the direction of the subsequent signal based on the signal, avoid the sound of the headset "crashing" when opening and closing the car door, and achieve the safety of the protection system, as well as better protect the user's hearing. It is worth mentioning that the cost-effective solution ADAU1788 is also on the market, which will help such solution products cover the mid-end market. </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> Although these features can help achieve product differentiation first, the product performance advantage will depend on the customer's product definition and acoustic characteristics research, which is not a low threshold for most small and medium-sized customers. "We will help customers solve chip application problems, and we also have experienced third-party partners who can provide very professional support, such as Beijing HT Acoustics and Dongguan ASKA, who can provide a complete turn-key solution." Sophie Mao said this. Speaking of technical support, ADI's free audio processor programming, development and debugging software Sigma Studio tool has to be mentioned. The tool provides a variety of signal processing algorithms integrated into an intuitive graphical user interface (GUI), which can create complex audio signal flows. For customers who do not understand programming but are proficient in acoustics, they can also use this software to easily complete tasks. "Sigma Studio is also a good online real-time tuning platform. All our customers do preliminary development based on Sigma Studio, including completing prototype design." Sophie Mao added. </span> </p> <p style="line-height: 1.75em;text-align: center;"> <span style="font-size: 14px;"> </span> </p> <p style="line-height: 1.75em;text-align: center;"> <span style="color: rgb(127, 127, 127);font-size: 12px;"> SigmaStudio Graphics Development Tool </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <div data-id="98604" data-tools="135编辑器"> <div style="margin: 10px auto;text-align: center;"> <div style="display: inline-block;"> <div style="color: rgb(12, 167, 210);display: flex;justify-content: center;align-items: center;padding-right: 3px;padding-left: 3px;margin-right: auto;margin-bottom: -2px;margin-left: auto;"> <div data-brushtype="text" style="letter-spacing: 2px;font-size: 16px;font-weight: bold;"> <span style="font-size: 14px;"> ANC technology is popular in the "headphone circle", and more application scenarios are discussed </span> </div> <div style="width: 30px;margin-left: 5px;"> <div style="width: 30px;"> </div> </div> </div> <div style="height: 1px;background-color: rgb(12, 167, 210);flex: 1 1 0%;margin-right: 40px;color: rgb(255, 255, 255);overflow: hidden;"> <br/> </div> <div style="height: 1px;background-color: rgb(12, 167, 210);flex: 1 1 0%;margin-top: 2px;color: rgb(255, 255, 255);overflow: hidden;"> <br/> </div> </div> </div> </div> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> In fact, ANC technology is not only popular in TWS headset applications, but has also gradually "gone viral" and is used in three-dimensional open sound fields for active noise reduction. In addition to excellent active noise reduction algorithms, this requires a deep acoustic theory background to model, analyze, simulate, and reduce noise in three-dimensional sound fields, so as to achieve active noise reduction in specific areas without wearing them, thereby greatly expanding the scope of application. </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> At present, the application of three-dimensional active noise reduction technology is more mature in the car cockpit. Generally speaking, in addition to the noise mainly coming from the engine, there are also noises including tire noise, wind noise and external environment when the vehicle is driving. The purpose of noise cancellation is achieved through similar noise collection, noise spectrum analysis and anti-phase noise elimination. Not long ago, ADI and Hyundai Motor Company cooperated to launch the industry's first fully digital road noise reduction system. The core part of the system uses ADI's A²B audio bus technology to solve the key challenge of electronic acquisition signal transmission delay; relying on DSP algorithms to ensure the independence of sound zones in different positions in the car and achieve echo cancellation, and cooperate with the microphone amplifier for ANC active noise reduction. </span> </p> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> In addition, with the comprehensive upgrading of consumption today, there is a strong demand for noise reduction technology in the field of home appliances, but the application and layout are still a blue ocean. As the main focus of the home market, various noises such as blenders, vacuum cleaners and toasters bother many consumers. At CES2020 at the beginning of this year, ADI demonstrated the active noise reduction function of home appliances (coffee machines) based on the ADAU1452 audio processor, which can achieve a 10dB noise reduction effect. Such solutions can also be applied to home appliances that generate louder noise, such as soybean milk machines, range hoods, etc., to make uncomfortable noises disappear from the home environment. </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <p style="line-height: 1.75em;text-align: center;"> <span style="font-size: 14px;"> </span> </p> <p style="line-height: 1.75em;text-align: center;"> <span style="color: rgb(127, 127, 127);font-size: 12px;"> ADI demonstrates using its SigmaDSP to suppress coffee machine noise at CES2020 </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> In fact, innovation based on ANC is far more than that. The ubiquitous noise and people's pursuit of a comfortable environment have created a huge space for innovative application of ANC technology. "ANC technology can also be used in hearing aids. By receiving specific sounds in a similar selective transparency mode and combining bone conduction related technology, people with hearing impairments can be equipped with sound collection and amplification devices similar to ANC to help them hear sounds and improve their perception of external sounds. This is also a future application development trend." Sophie Mao added another innovative product application. </span> </p> <p style="line-height: 1.75em;"> <br/> </p> <div data-id="98604" data-tools="135编辑器"> <div style="margin: 10px auto;text-align: center;"> <div style="display: inline-block;"> <div style="color: rgb(12, 167, 210);display: flex;justify-content: center;align-items: center;padding-right: 3px;padding-left: 3px;margin-right: auto;margin-bottom: -2px;margin-left: auto;"> <div data-brushtype="text" style="letter-spacing: 2px;font-size: 16px;font-weight: bold;"> <span style="font-size: 14px;"> Conclusion </span> </div> <div style="width: 30px;margin-left: 5px;"> <div style="width: 30px;"> </div> </div> </div> <div style="height: 1px;background-color: rgb(12, 167, 210);flex: 1 1 0%;margin-right: 40px;color: rgb(255, 255, 255);overflow: hidden;"> <br/> </div> <div style="height: 1px;background-color: rgb(12, 167, 210);flex: 1 1 0%;margin-top: 2px;color: rgb(255, 255, 255);overflow: hidden;"> <br/> </div> </div> </div> </div> <p style="line-height: 1.75em;"> <span style="font-size: 14px;"> 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 the TWS Bluetooth headset market, traditional headset brands are making great efforts, and emerging headset brands are advancing rapidly, which will inevitably drive the differentiation of the TWS market to accelerate. The prices of mid-to-high-end products with lower costs and stronger performance will fall due to economies of scale, allowing more people to enjoy the charm and fun of technology, which is also the direction of ADI's efforts. </span> <span style="font-size: 14px;"> According to Sophie Mao, ADI will continue to strengthen differentiation in the lightweight, low power consumption, low cost and high performance of TWS headset ANC technology to cover more terminal markets. </span> <span style="font-size: 14px;"> "The use scenarios of related products supported by ANC technology are becoming more and more abundant. Modular solutions like those provided by ADI can also empower a new wave of innovative applications and help customers stay at the forefront of technology. </span> <span style="font-size: 14px;"> " </span> </p> <div> <div style="margin: 10px auto;"> <div> <div style="display: flex;justify-content: flex-start;"> <div data-width="45%" style="width: 45%;height: 8px;background: rgb(12, 167, 210);margin-bottom: -8px;overflow: hidden;"> <br/> </div> <div style="width: 0px;height: 1px;border-top: 8px solid rgb(12, 167, 210);border-right: 8px solid transparent;margin-bottom: -8px;overflow: hidden;"> <br/> </div> </div> <div style="border-width: 8px;border-style: solid;border-color: rgb(235, 238, 237) rgb(235, 238, 237) rgb(235, 238, 237) rgb(12, 167, 210);"> <div style="display: flex;justify-content: space-between;align-items: center;padding: 15px;"> <div style="width: 100px;"> </div> <div style="padding: 15px;"> <p style="text-align: center;font-size: 12px;word-break: break-all;"> Scan the QR 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