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Active noise cancellation has become a new selling point for headphones, but the noise reduction performance of different headphones varies greatly. Recently, the State Administration for Market Supervision and Administration for active noise reduction headphones for risk monitoring, involving 60 pairs of headphones, the test results show that 50% of the noise reduction is insufficient, there may be a certain risk of hearing damage. Why does the noise-canceling performance of active noise-cancelling headphones make such a big difference? The main reason is mainly concentrated in three aspects: engineering design, procurement quality control, and noise reduction algorithm.
<b>Engineering design: shape design and cavity design</b>
Samsung Galaxy Buds Pro Bluetooth True Wireless Active Noise Cancelling Headphones - Compared to galaxy Buds+ headphone size
HUAWEI Huawei FreeBuds 4 Bluetooth True Wireless Active Noise Cancelling Headphones
In the engineering design of active noise-canceling headphones, if it cannot match the ear canal and wearing mode of most people, it will lead to various sound leakage problems, resulting in external noise transmitted through the earbuds to the ear, so its active noise reduction ability will be greatly reduced. As a typical example, even Huawei's FreeBuds 4, a product that Huawei wants to do wonders, is weaker than other in-ear or headsets due to its semi-in-ear design. On the other hand, it lies in the cavity design, and the change of the cavity design will bring about changes in the speaker and microphone signals, which in turn will affect the noise reduction effect.
Cheap or even white-label products of the mold is relatively rough, although there is a standard answer - AirPods Pro, but it is inevitable to encounter problems such as insufficient assembly accuracy, white-label manufacturers change the design, brand manufacturers for the low-end product cavity optimization may not be as good as high-end products, resulting in differences in noise reduction performance.
<b>Procurement quality control: component consistency level and parameter performance</b>
Active noise reduction needs to be implemented based on hardware, but if the performance of this set of hardware is uneven, it will lead to a "lottery" of noise reduction performance. The principle of active noise reduction is very simple, that is, the ambient noise is monitored by the microphone, and then the noise curve is analyzed by the processing chip, and then the speaker generates reverse sound waves to cancel out the external noise. The problem of differences in noise reduction ability occurs on microphones and speakers here.
Silicon Wheat [Image from the Internet]
Active noise-canceling headphone microphones require higher signal-to-noise ratios, sensitivity, and consistency. The microphone needs to collect and restore as much external audio information as possible, if the sensitivity and signal-to-noise ratio are not high enough, it may lead to insufficient sampling of external noise and limited noise reduction ability. Sony supplier Xingang Electronics said that high-end noise reduction products will use microphones with SNR more than 70 or even higher in the design to ensure noise reduction. For comparison, according to Howey Technology data, the SNR (signal-to-noise ratio) value of MEMS products in the industry is generally 62dB, the sensitivity is analog silicon wheat: -38/-42±3dBV, digital silicon wheat: -22/-26± 3dBFS.
MEMS microphone [image from the network]
Another issue is consistency, where active noise cancellation performance requires higher sensitivity and phase consistency. Active noise cancellation is to counteract external noise by generating reverse sound waves, if the consistency of the left and right ears for noise reduction sampling, the consistency of the microphone inside and outside the ear canal is not enough, the noise reduction performance will also be greatly reduced, for example, the same MEMS microphone, twice on the side of high sensitivity, on the other side of the low sensitivity, the algorithm listens to whom? In general, the sensitivity consistency should reach a range of +/- 1dB to achieve better noise reduction, and the above data indicates that the ordinary microphone sensitivity is +/- 3dB.
Another example is speaker performance, because active noise cancellation is to reverse the noise, so the speaker of the active noise cancellation headphones needs a large dynamic (>120dB) and fast transient response to react to external noise faster, and then reverse cancel. So in theory, noise-canceling headphones also have Hi-Fi potential. Shenzhen Xinlian Ruichuang, a provider of noise reduction solutions, said that the curve of the frequency response of the speaker must be flat, especially in the low-frequency part, the smaller the speaker distortion, the better
Headphone speaker diaphragm
To achieve a microphone with a high signal-to-noise ratio, high sensitivity, high consistency, and a loudspeaker with high dynamics and fast transients, it is actually not difficult, just add money. However, white-brand headphones and low-end products began to compress costs in hardware procurement, especially the single batch of Huaqiang North white-label headphones had a small purchase volume and weak bargaining power, and it was more difficult to purchase high-standard, high-consistency components. This is also the reason why there is a difference in ear noise reduction between the left and right ears of individual products mentioned in the news.
<b>Algorithm design</b>
White-card and low-end headphones usually do not customize the algorithm separately, just use the whole set of solutions, many solutions are from chip vendors, but these solutions are not adaptable enough in software and hardware. In addition, the performance of the low-end chip in terms of noise reduction is also weaker than that of high-end products, such as cache size, DSP performance, etc. Hengxuan BES2500 series has dual-core M33 and 400MHz DSP in order to reduce noise. Big-name headphones are usually individually customized to match their own hardware and software designs for targeted optimization.
In engineering design, procurement quality control, noise reduction algorithms, these three aspects, Huaqiang North AirPods Pro is weaker than the brand manufacturers in the low-end products, brand manufacturers in the low-end products are weaker than their own high-end main force, of course, the strongest in this aspect, there is no doubt that Apple. Therefore, if Ni Meng wants to buy a Huaqiang North AirPods Pro, buy to play and experience the experience is no problem, as for noise reduction, just use the lottery, really want to achieve excellent noise reduction, or have to buy big-name main products.
[Doc]key=TWS active noise reduction[/Doc]