Lei Feng network (search "Lei Feng network" public concern) by: The author of this article Chen Xiaoliang, doctor of engineering, the founder of Sound Technology. Lei Feng network article, reproduced please contact the authorization. Apple's new iPhone7/iPhone7 Plus has just shipped, and recently it has exploded. There are already a lot of fruit powders that reflect the iPhone 7/7 Plus will be issued in the case of work under heavy load "buzz." Stephen Hackett first posted this question on Twitter and uploaded a video to confirm his claim. Stephen's complaint has been confirmed by many fruit powders, including former Apple publicist and Darrell Etherington, editor of TechCrunch, after many users have commented that they have the same situation. This issue has just exploded. It is estimated that Apple has not yet confirmed the cause. However, Apple has already given its commitment to replace the new one. Foreign media speculated that this "buzz" may be related to Apple's A10 Fusion processor, the reason being that this noise only appears when the CPU load is large . Most of the domestic fruit powder has not yet got a new machine. For the time being, it cannot be tested in real machine. According to the reflection of foreign fruit powder, it is also a problem that only a small number of mobile phones appear. But what exactly is this "buzz"? First listen to this "click" uploaded by Stephen Hackett. We extracted from the video the “squeaks†taken by Stephen Hackett. Although there were other noises during the recording, it was still very similar to the “HISS†feature. “HISS†is also known as “click†and is a common noise. Many times we refer to it as “current noise†. Actually, “HISS†noise is difficult to describe accurately. This kind of noise is common in electronic products such as computers, televisions, air conditioners, refrigerators and other electronic devices, but other noises of these devices are more obvious and are often ignored due to the masking effect of the human ear. However, devices such as mobile phones, speakers, headphones, radios, and chargers are very close to the user, so their "clicks" are also common complaints. Stephen Hackett's "Bark" Time-frequency Distribution "HISS" is an internationally popular "squeak" description. This noise is similar to Gaussian white noise, its amplitude distribution obeys Gaussian distribution, and power spectral density obeys uniform distribution. The white noise actually borrows the concept of the spectrum, which is the same as the white light formed by the superposition of light of all colors, and the white noise can also be understood as the superposition of sounds of all frequencies. The Gaussian white noise sounds in the audible band are very similar to the iPhone 7's "squeak". Interested readers can use Matlab's WGN function to generate Gaussian white noise, or analogous to the car radio when searching for channels. Humming." The noise of electronic devices mainly consists of three sources, mechanical noise, electromagnetic interference, and circuit noise. Many times, these three types of noise are mixed (linear or nonlinear). Mechanical noise is generally caused by the mechanical vibration of the alternating device. This kind of noise is generally more obvious at low frequencies, and sounds like “when it's awakeâ€. Electromagnetic interference is mainly caused by high-frequency devices, especially RF devices (mobile phone RF) will have a greater impact on the surrounding analog lines. Therefore, mobile phone designs often require electromagnetic shielding (metal casing) of high-frequency devices, or components that have been specially designed for electromagnetic shielding. For example, the microphones and speakers used in the iPhone have been designed to prevent RF. The circuit noise mainly refers to the white noise of the electronic equipment and basically comes from thermal noise and shot noise. The thermal noise mainly originates from passive devices such as the electronic Brownian motion of resistors, and shot noise originates from active devices. For example, the electron emission non-uniformity of a semiconductor device. "Beep" is a common circuit noise, similar to Gaussian white noise, and theoretically exists in any electronic device, but the frequency of digital devices is higher than the human ear can hear 20KHz, so we heard "Sound" mainly comes from analog circuits, such as op amps and inductors are more likely to produce "buzz." It should be noted that the reason for the "clicking" generated by the inductor is more complicated, and the influence of the alternating current must also be taken into account. The source of some devices "clicks" is mainly the inductor, for example, many chargers with poor quality. Based on the above analysis, iPhone 7's "click" should not be a hardware design flaw, and the relationship with the CPU will not be too much, the CPU is a high-frequency device, and rarely integrate analog circuits . This kind of sound occurs when the load of the CPU is relatively large. It may be related to power or temperature. The generation of thermal noise is closely related to the temperature, and the probability of hearing a “click†is also higher when the power is increased. , especially for some poor quality electronic devices. iPhone 7's "buzz" may be the largest possible source from the op amp, inductors and other analog devices, these devices used in a large number of mobile phones, including power management, camera circuit, microphone circuit and speaker circuits and so on. Although it is difficult to locate the cause of the failure based on current information alone, it is estimated that the problem will not be too serious, and it should be the small-scale incident caused by the quality of some of the iPhone 7's electronic components . In fact, the quality management of the supply chain is a headache for all hardware manufacturers. The number of components on a mobile phone is huge, and most of the components can only be spot-checked. This makes it impossible to achieve 100% device qualification, even if it is famous. The same is true of the factory. The reliability of the hardware device is not defective in design, but if the reliability of the device is not enough, even a single component may cause serious consequences, such as the recent Samsung battery explosion. Vendors engaged in hardware everywhere are pits, and are also the main reason why many Internet companies in China are unable to make hardware.
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