The principle of noise canceling headphones（part 1）

When you wear a specially designed earphone, external noise will no longer cause interference to you.

This is the enjoyment brought to us by noise-canceling headphones.

Why can noise-canceling headphones have such a magical performance?

This article will take you into the world of noise-canceling headphones.

Classification of noise-cancelling headphones 

Headphones that can effectively reduce environmental noise are called noise-cancelling headphones. Objectively speaking, almost all earphones have considered how to reduce external noise at the beginning of the design, but noise reduction earphones have carried out more consideration in reducing noise and have more prominent performance.

According to the principle, noise reduction headphones are mainly divided into two types: one is passive noise reduction (Passive Noise-Cancelling) headphones, and the other is active noise reduction (Active Noise-Cancelling) headphones. The so-called passive noise reduction earphone is to isolate noise as much as possible through the soundproof material or special structure on the earphone.

Earphones with in-ear earbuds and large earmuffs that we have introduced before can be classified as passive noise-cancelling headphones. Even the active noise-cancelling headphones we study below have also added the design of passive noise-cancelling headphones. Of course, these do not have strict boundaries, because there is only one purpose: how to reduce environmental noise more effectively.

The active noise reduction headset is a special noise reduction circuit set in the headset. Generally, an audio receiver (such as a miniature microphone) and an anti-noise output chip are used to receive and analyze the frequency of external noise and generate the opposite frequency to weaken or cancel each other, so as to achieve the purpose of shielding noise.

The process from the beginning of the operation of the active noise reduction headset to the hearing of the human ear can be divided into several steps. First, the miniature microphone placed in the headset collects the mid/low frequency noise in the environment that the ear can hear   (such as 100Hz)

1000Hz); Next, the noise signal is transmitted to the noise reduction circuit, and the noise reduction circuit performs real-time calculation; after the noise reduction circuit is processed, the generated signal is generated through the speaker to cancel the noise by generating a sound wave with the opposite phase of the noise and the same amplitude; Eventually, our ears will feel the noise is reduced or even disappeared.

In short, it is to use a micro microphone to collect noise, through the noise reduction circuit to reverse the phase of the noise by 180 degrees, and produce the corresponding anti-noise to cancel each other. Generally speaking, the effect of active noise reduction headphones is very obvious.