What is the principle of noise reduction in headphones? Is it necessary?

Do you know how noise-canceling headphones work?

Does the world get on your nerves? When you want to listen to a quiet person, there is always that annoying laughter, noise, girlfriend’s nagging voice. Do you want to escape them? That’s where noise-canceling headphones come in. People can be immersed in their own world, enjoy the vibration of the heart. Do you know how noise-canceling headphones work?

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K8-Headphones noise reduction

Today, I will, as always, give you a popular science: the principle of noise-canceling headphones, and write some thoughts, personal opinions and recommendations. In fact, there are two ways of noise reduction: active noise reduction & passive noise reduction

01 Active noise reduction

Generally speaking, it is necessary to build a noise reduction module in the earphone, including a microphone, to accept noise, and then after the calculation of the internal circuit, when the earphone plays music, add the sound wave that rotates 180° with the signal of external noise, so as to cancel the external noise. However, active noise reduction also falls into three different technologies.

The feedforward ANC uses a feedforward noise control system (open-loop noise control system), which requires the sound information of the primary sound field to be controlled, often referred to as the reference signal.

The reference signal is sent to the feedforward controller, and after calculation by the built-in processor, an opposite control signal will be generated, which will drive the loudspeaker to output the sound signal to generate the secondary sound field, and then superimpose and cancel the noise signal transmitted by the physical way.

The error microphone detects the error signal formed by the superposition of the primary and secondary sound fields and sends it to the processor, which adjusts the intensity of the secondary sound source signal according to the algorithm.

headphones noise reduction

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The system is an open loop, so it can be adjusted independently without causing any closed-loop oscillations and squeaks. And the microphone in the headphone in the front can be much earlier than the human ear to receive noise, system processing more timely

It is only responsible for reporting to the noise reduction circuit, and then monitoring other sounds, unable to deal with the residual noise inside the headset after noise reduction (the most typical is the wind).

Using a feedback active noise control system (closed-loop noise control system), the feedback system has fewer reference microphones than the feedforward system, so the structure is simplified. The feedback structure of the active noise control system does not get the sound information in advance but adjusts the error signal through the processor, so as to reduce the noise.

When the gain of the amplifier is increased to a certain extent, it will become very unstable, producing high or low-frequency noise. In order to maintain its stability, the controller and the error microphone are generally required to be very close to each other, but it also leads to a greatly reduced range of feedback applications.

SN-017 Gaming in-ear Earphones
SN-017 Gaming in-ear Earphones

Advantages: When hearing the noise, it will detect and deal with the noise many times, the noise processing effect will be better

Disadvantages: the position of the controller and the error microphone is too close, the reaction time is relatively short, and the closed-loop noise control system is easy to produce high-frequency noise or low-frequency oscillation.

Hybrid ANC (Doubly-fed active noise reduction, Hybrid active noise reduction)

This is the best noise reduction design (or one?) on the market right now. , its secondary sound source will be determined by the reference microphone and the error microphone.

The feedforward system can attenuate most of the noisy noise, while the feedback system only deals with the residual noise inside the headphones. These two things work so well together!


Advantages: combine the advantages of the above two noise reduction methods, with the most excellent noise reduction effect!

Disadvantages: the volume is a little bit, and the design is difficult, the cost is not low. So the headphones are generally more expensive

02 Passive Noise reduction

Passive noise-canceling earphones mainly surround the ears to form a closed space or use silicone earplugs and other sound insulation materials to block outside noise. Because the noise has not been processed by the noise reduction circuit chip, generally can only block the high-frequency noise, the low-frequency noise reduction effect is not obvious (you try to cover your ears with your hands?)

Advantages: Because of the principle of active noise reduction, nature will have more or less loss of sound quality, while this core noise reduction,

Disadvantages: Stethoscope effect, noise cancellation unclean, etc….

Passive Noise reduction

headphones noise reduction

03 Noise-cancelling headphones necessary?

It depends, since active noise-canceling headphones are generally relatively expensive, it doesn’t matter if you don’t often listen to headphones in noisy places. But noise-canceling headphones are undeniably useful

But in an era of increasingly mobile phones, face-to-face communication has become difficult, a large proportion of young people have social phobia (me included), plus a noise reduction is completely “aloof”. That’s why I traded my old Airpodspro for buds,

Remove both earmuffs and place them in a small airtight bag. Drop alcohol and soak in the earmuffs. Let it sit for a while and let it dry. Once a week is recommended.

You may have heard this a lot, but I want to say this to you:

Protect your ears and turn them down. Spend more time with family and talk to friends. People are social creatures after all. What mood is not good to listen to the song, but is the depression deep-buried just, find a friend hard scold a good.

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