Noise Reduction Technology - ANC, ENC, DSP, CVC

Noise reduction refers to the use of a method to reduce noise.

At present, there are two kinds of noise reduction technology: active noise reduction and passive noise reduction.

Active Noise Cancellation（ANC）

The active noise reduction function is to generate reverse sound waves equal to the external noise through the noise reduction system, neutralize the noise, and achieve the effect of noise reduction.

Active noise reduction refers to collecting some regular noises from the outside world (such as the roar of aircraft engines) through noise pickup microphones in some specific occasions, such as high-speed rails/airplanes. Through the circuit or algorithm, the reverse noise signal is added to the music signal, and the sound in the earphone heard by the human ear is directly offset from the external noise, so as to achieve the noise reduction effect.

Passive Noise Reduction

Passive noise-cancelling headphones mainly block external noise by surrounding the ears to form a closed space, or using sound insulation materials such as silicone earplugs.

This refers to in-ear earplugs, because the earplugs are inserted into the ear canal of the human ear through a silicone sleeve. Therefore, it has a better function of isolating external sounds. And this noise reduction is full frequency, that is, it is effective for sounds from 20 Hz to 20K Hz, and this passive noise reduction is lossless sound quality. So the general HiFi earbuds are in-ear for this reason.

Call Noise Reduction

Call noise reduction refers to the fact that when the Bluetooth headset is used for a call, it is designed so that the other party of the call can hear it clearly. Common such as Qualcomm's CVC noise reduction. Its principle is to use the chip inside the Bluetooth headset to filter the signal received by the call microphone to reduce the wind noise from the outside world. At the same time, it can also perform echo reduction processing on the call sound transmitted by the other party. Since CVC noise reduction does not have an additional microphone to collect external noise, the noise reduction effect is still not enough for practical applications.

Therefore, some Bluetooth headsets are also designed with additional microphones to collect ambient noise, and then the internal processor will subtract the external noise collected by the noise pickup microphone from the signal collected by the call microphone. So this noise reduction effect is much better. This kind of noise reduction is generally called "upstream noise reduction".

At present, the active noise reduction in the headphone market is ANC, ENC, CVC, DSP and other noise reduction technologies.

ANC

The working principle of ANC noise reduction (Active Noise Control, active noise reduction) is that the microphone collects external ambient noise, and then the system transforms it into an inverted sound wave and adds it to the speaker end. The final sound heard by the human ear is: ambient noise + anti-phase The two kinds of noise are superimposed to achieve sensory noise reduction, and the beneficiary is yourself.

ENC

ENC (Environmental Noise Cancellation, environmental noise reduction technology) can effectively suppress 90% of the reverse environmental noise, thereby reducing the environmental noise by up to 35dB, allowing gamers to communicate more freely. Through the dual-microphone array, the direction of the caller's speech is accurately calculated, and various interfering noises in the environment are removed while protecting the target voice in the main direction. HYXKIOT QCC5125 Bluetooth audio module HY-BT301C support ENC and DSP noise reduction technology.

DSP

DSP is the abbreviation of English (digital signal processing digital signal processing). Mainly for high and low frequency noise. The working principle is that the microphone collects the external environmental noise, and then the system replicates a reverse sound wave equal to the external environmental noise to cancel the noise, so as to achieve a better noise reduction effect. The principle of DSP noise reduction is similar to that of ANC noise reduction. However, the forward and reverse noises of DSP noise reduction directly neutralize and cancel each other within the system.

CVC

CVC (Clear Voice Capture) is a noise reduction technology for call software. Mainly for the echo generated during the call. Through the full-duplex microphone noise cancellation software, it provides the function of echo and ambient noise cancellation for calls, which is the most advanced noise reduction technology in the current Bluetooth call headset.