Recently, "only 2 noise-canceling headphones have been certified by the Ministry of Industry and Information Technology A", which has been on the hot search. According to CCTV reports, nearly 50% of the noise reduction headphones are insufficient. As a result, it triggered a big discussion among netizens on the reliability of noise-canceling headphones: Which noise-canceling headphone brands participated in this test? Have brands with a large user base in noise-cancelling headphones been detected? Are the noise-cancelling headphones you buy "pseudo-noise reduction"?
According to the official website of the National Industrial Information Security Development Research Center, after evaluation, stroller TWS NB2, wanderer NeoBuds Pro, OPPO Enco Free2i, OnePlus Buds Pro a total of 4 products have obtained the smart noise reduction headset product user scenario ANC (active noise reduction) comprehensive noise reduction A level evaluation certificate, not the "only 2 models" mentioned in the hot search.
It can be seen from the "Notice on Carrying out Intelligent Noise Reduction Headset Product Scene Evaluation Activities" initiated by the National Industrial Information Security Development Research Center that this round of evaluation and solicitation launched in November 2021 requires enterprises to self-declare according to the main business products. Therefore, the 4 products that have obtained the A-level evaluation certificate are based on "self-declaration" and "domestic brands", while many well-known brand products such as Apple and Huawei are not in this sample pool. At present, the national noise reduction headphone manufacturers according to statistics more than 300, the product is countless, this evaluation does not mean that other noise reduction headphone products must not meet the A-level evaluation standards, less sample size, in fact, can not draw the conclusion that "only 2 models have obtained A-level certification", this statement is misleading to consumers. It is understood that at present, no government department has taken the initiative to organize large-scale TWS noise reduction headphone evaluation.
The "Finance world" weekly found that CCTV did report in July 2021 that nearly half of the active noise cancellation headphones were insufficient in noise reduction. The report is more to remind consumers that noise-canceling headphones have insufficient noise reduction and there is a risk of hearing loss. The State Administration for Market Regulation has tested 60 pairs of headphones from 47 companies, using relevant standards for the EUROPEAN Union and the military.
But most of these headphones are wired noise-cancelling headphones. A headphone manufacturer said that the relevant agencies for the TWS active noise reduction headphone standards also recommend keeping pace with the times, need to consider the difference between TWS active noise reduction headphones and traditional wired active noise canceling headphones in the scene. The implication is that the problem of nearly 50% of the noise reduction of noise reduction headphones reported by CCTV is the traditional detection standard with a higher level, and the current TWS headphone industry is not perfect and unified enough for active noise reduction standards.
What is the principle of noise-cancelling headphones?
Speaking of the principle of noise-canceling headphones, we must start with ANC noise reduction technology. The earliest ANC noise reduction technology was a U.S. patent filed by Paul Lueg in 1936 for noise cancellation in pipes. The patent diagram at that time is as follows:
Since 1955, the industry has been studying ANC headphones. In 1989, Dr. Bose could not stand the noise of aircraft, so he developed the first real ANC headphones, and then ANC began to transition from professional aviation and military fields to audiophile headphones.
Tall on aviation-grade noise-cancelling headphones
However, for a long time since ANC entered the civilian market in 2000, ANC technology has not been popularized, importantly because of the high price. In 2014, BOSE released the QuietComfort 20, which made the market begin to accept ANC technology. In recent years, with the hot sales of TWS headphones, after Apple AirPods Pro added ANC functions in 2019, ANC has rapidly evolved from headphones to the TWS market and further entered the public vision.
BOSE QuietComfort 20
Noise reduction can be divided into active noise reduction and passive noise reduction according to the principle, passive noise reduction is simply through physical means to isolate the transmission of sound, such as earplugs or head-mounted ear - which can still be seen from airport ground staff to this day. Physical isolation is limited by the characteristics of sound frequencies, which can only isolate frequencies above 1kHz, and frequencies below 1kHz can still be transmitted to the eardrum through the ear cups or the human body.
Active noise reduction technology takes advantage of the characteristics of acoustic mechanical waves, and the system actively generates a signal opposite to the noise, which cancels out the noise and eliminates the noise. Active noise reduction can be divided into analog noise reduction technology and digital noise reduction technology according to different circuits.
Among them, analog noise reduction technology is built through the op amp, resistance capacitance and other circuits, with low latency, low cost and other characteristics, while the digital noise reduction technology is through ADC sampling, DSP digital filtering, DAC output of digital technology to process noise, with small size, easy calibration, high quality, support for a variety of algorithms and other characteristics, and because of the built-in calibration function, there is no need to calibrate after production like analog circuits, thus reducing the cost of the entire product production process. As processing speeds increase, the latency of the digital ANC becomes lower and lower, almost negligible compared to the total latency of Bluetooth.
According to the location of the acquisition microphone, it can be divided into three ways: feedforward, feed-back and hybrid ANC.
As shown in the figure, the feed-forward network is an open-loop network, there is no feedback but the noise reduction depth is not enough, and it can only support noise reduction of about 1x dB. The feed-back network supports sound monitoring after noise reduction, so it can do noise suppression again, which can achieve more than 30dB noise reduction, but the frequency band is short. The hybrid type selects two microphone samples at the same time, so it can meet the characteristics of wide band and large depth at the same time, but the design is difficult and the cost is higher.
For example, B&W's noise-cancelling headphones use hybrid ANC technology to make it have excellent ANC functionality.
How harmful are unqualified headphones
CCTV said that nearly 50% of the noise reduction headphones are insufficient, there is a phenomenon of unqualified, which ones are included, and it is not stated for the time being. If you want to protect your hearing, you still want to choose the authoritative brand of the Ministry of Industry and Information Technology for the detection and evaluation of headphones.
So how harmful is substandard headphones? Listening to music, watching dramas, playing games, sports and fitness, etc., wearing headphones has become normalized, but wearing unqualified headphones or long-term wearing unqualified headphones will definitely have an impact. From a scientific point of view, there are at least two major hazards that can be done.
First, directness causes hearing damage. As we all know, when we put on the headphones, almost the entire hearing system is shrouded. The inner ear hair cells located in the cochlea position are the main "power generators" of the entire hearing system, transmitting external sounds to the auditory nerve. If you use the headphones for a long time without reason, and if you use substandard headphones, it may lead to damage to the ear hair cells in the ears.
According to scientific arguments, ear hair cells are limited, and belong to the "non-regenerative" model, then when used, if the period is in a state of exhaustion and damage for a long time, it may lead to hearing loss, and an irreversible situation, which may eventually lead to loss of hearing.
Second, it causes ear diseases and may eventually lose hearing. Wear headphones for a long time, the air does not circulate, and the headphones are not qualified to carry some bacteria, etc., if not cleaned in time, it may lead to bacterial infection in the ears, if the chain effect is triggered, there may be eardrum damage, tinnitus and other phenomena, which may eventually lead to hearing loss or loss of hearing, which is the general situation.
According to the WHO Report on Ear Day on 3 March 2020, in addition to the innate environmental impact, 1.5 billion people worldwide are currently facing hearing impairment due to increased environmental noise and unscientific and reasonable ear use. Therefore, when we buy noise-canceling headphones, we should buy a nationally certified, compliant, and inspected high-quality product to use.
Source: Web Content Synthesis