What are noise-canceling headphones?

There are two methods for earphone noise reduction, active noise reduction and passive noise reduction.

The active noise reduction function is to generate a reverse sound wave equal to the outside noise through the noise reduction system, neutralize the noise, and achieve the effect of noise reduction. Active noise-canceling headphones have a noise-reduction circuit that counteracts external noise. Most of them use a larger head-mounted design. They can use earplug cotton and headphone shells to block external noise and perform the first round of sound insulation. There is ample space to install active noise reduction circuits and power supplies.

Passive noise-cancelling headphones mainly form a closed space by surrounding the ears, or use soundproof materials such as silicone earplugs to block external noise. Since the noise has not been processed by the noise reduction circuit chip, it can generally only block high frequency noise, and the noise reduction effect on low frequency noise is not obvious.

The three noise reduction measures commonly used to reduce noise, namely noise reduction at the sound source, noise reduction during propagation, and noise reduction at the human ear, are all passive. In order to actively eliminate noise, people invented the "active noise reduction" technology. Its principle is: all sounds heard are sound waves and have a certain spectrum composition. If you can find a sound wave whose spectrum is equal to the amplitude of the noise to be eliminated, and the phase is exactly opposite (a difference of 180°), the superposition of the two can completely cancel the noise. The key is how to get the sound that cancels the noise. The actual method used is to start with the noise itself, use a microphone to monitor the noise, and then try to generate a reverse sound wave through the electronic circuit and play it through the speaker. From this point of view, the technology of active noise reduction is actually "fighting poison with poison."

When dealing with complex noise environments, the two "active noise reduction" MEMS microphones will pick up the noise in the ear and various external environment noises respectively, and are equipped with an independent intelligent high-definition noise reduction processor to perform high-speed calculations on the different noises picked up. Precise noise reduction. And in response to the noise reduction requirements of different scenarios, the headset provides a variety of listening modes: two active noise reduction modes, strong and weak, and an ambient sound mode. Isolate external noise to varying degrees, eliminating the "black hole" of common noise-reducing headphones when listening.

Application principle:

Noise-canceling headphones use active noise control, which is different from the passive sound insulation of general headphones. The principle is:

1. First detect the low-frequency noise (100~1000Hz) in the environment that the ear can hear by the signal microphone placed in the earphone

2. Pass the noise signal to the control circuit, and the control circuit performs real-time calculations

3. Use Hi-Fi speakers to play sound waves with the opposite phase and the same amplitude as the noise to cancel the noise

4. After superposition, the noise disappears and is inaudible

Suitable for the crowd:

*First of all, business people. Due to frequent business trips, especially business people who travel between different cities every day, they must hate the noise in the cabin the most. If there is a noise reduction headset, they must be able to stay away from these noises, and at the same time can relax by listening to music.

*Of course there are the subway people. Office workers who squeeze the subway every day have become accustomed to the noise in the subway, but at this time, if you can have a pair of noise reduction headphones, you can not only stay away from the noise, but also can adjust your mood through headphones and enjoy this happily process.

*The office workers also need a pair of noise-canceling headphones. Sometimes when thinking about the planning plan, listening to the sound of the central air-conditioning operation is particularly annoying, and it is even more annoying if there are colleagues around you who are constantly whispering. At this time, you might as well put on a pair of noise-canceling headphones and expand your mind in beautiful music.

What are the current active noise reduction technologies?

1.ANC noise reduction

ANC noise reduction (Active Noise Control, active noise reduction),

The working principle is to collect external environmental noise through the microphone, and then transform it into an inverted sound wave through the system and add it to the speaker. The final sound heard by the human ear is: environmental noise + inverted environmental noise, and the two noises are superimposed to achieve Noise reduction.

Pickup (monitoring environmental noise) → processing chip (analyzing noise curve) → speaker (generating reverberating sound waves) → complete noise reduction

2. ENC noise reduction

ENC (Environmental Noise Cancellation, environmental noise reduction technology),

Through the dual-microphone array, it accurately calculates the direction of the caller's speech, which protects the target voice in the main direction while removing various interference noises in the environment. It can effectively suppress 90% of the reverse environmental noise, thereby reducing the environmental noise up to 35dB or more.

The most obvious difference between ENC and ANC is that the beneficiary of ANC is the use of the headset. Through the function of ANC, users can protect themselves from environmental noise; the beneficiary of ENC is the other party on the call. The impact of the call allows the other party to hear the pure voice.

ANC makes the listening environment quieter, while ENC makes the listening environment at the other end of the call quieter.

3. DSP noise reduction

DSP is an abbreviation for English (Digital Signal Processing, digital signal processing).

The working principle is that the microphone collects external environmental noise, and then the system replicates a reverse sound wave equal to the external environmental noise to cancel the noise and achieve a better noise reduction effect.

The principle of DSP noise reduction is similar to ANC noise reduction. However, the forward and reverse noises of DSP noise reduction directly neutralize each other within the system.

The difference between DSP and ANC:

(1) Different types of aliased signals: ANC aliases acoustic signals, while DSP aliases digital electrical signals.

(2) The location of the aliasing is different: ANC is the aliasing of acoustic signals in the air from the speaker to the eardrum, while DSP is the aliasing of electrical signals within the earphone system.

4. CVC noise reduction

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 echo and environmental noise cancellation function of the call. It is the most advanced noise reduction technology in the current Bluetooth call headset.

The main beneficiary of DSP technology is the headset user, while CVC (Echo Cancellation) mainly benefits the other party on the call.