Noise reduction function is very important for headphones. One is to reduce noise and avoid over amplifying the volume, so as to reduce damage to the ears. Second, filter noise to improve sound quality and call quality. Noise reduction is divided into active noise reduction and passive noise reduction.
Noise reduction based on physical principles: headphones are used to expand and wrap the whole ear for passive noise reduction. They have high requirements for materials, poor air permeability and are not easy to dry after sweating. The in ear type is "inserted" into the ear canal to seal the ear canal for noise reduction. It is uncomfortable to wear for a long time, the pressure inside and outside the ear canal is uneven, and the wearing time should not be too long, which will affect the hearing.
Active noise reduction is achieved by analyzing the chip in the headset. The noise reduction sequence is:
1. First, the signal microphone placed in the earphone detects the low-frequency noise (100 ~ 1000Hz) in the environment that can be heard by the ear (up to 3000hz at present).
2. Then the noise signal is transmitted to the control circuit, which performs real-time operation.
3. The hi fi horn emits sound waves with opposite phase and the same amplitude as the noise to offset the noise.
4. So the noise disappears and can't be heard.
Active noise reduction is divided into ANC, ENC, CVC and DSP, so let's analyze what these English mean.
The working principle of ANC: (active noise control) is that the microphone collects the external ambient noise, and then the system transforms it into an inverted sound wave and adds it to the horn end. Finally, the sound heard by human ears is: ambient noise + inverted ambient noise. The two kinds of noise are superimposed to reduce the sensory noise, and the beneficiary is himself. Active noise reduction can be divided into feedforward active noise reduction and feedback active noise reduction according to the position of pickup microphone.
Enc: (environmental noise cancellation) can effectively suppress 90% of the reverse environmental noise, so as to reduce the environmental noise up to more than 35dB, so that game players can communicate more freely. Through the dual microphone array, accurately calculate the speaker's speaking direction, and remove all kinds of interference noise in the environment while protecting the target voice in the main direction.
CVC: (clear voice capture) is the noise reduction technology of call software. Mainly for the echo generated during the call. Through the full duplex microphone denoising software, it provides the echo and ambient noise elimination function of the call. It is the most advanced noise reduction technology in the Bluetooth call headset at present.
DSP: (digital signal processing) is mainly aimed at high and low frequency noise. The working principle is that the microphone collects the external environment noise, and then the system copies a reverse sound wave equal to the external environment noise to offset the noise, so as to achieve better noise reduction effect. The principle of DSP noise reduction is similar to ANC noise reduction. However, the forward and reverse noise of DSP noise reduction are directly neutralized and offset each other within the system.
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Original link: https://blog.csdn.net/momo1996_233/article/details/108659040
Post time: Mar-19-2022