How do noise cancelling headphones work?

by sogrow team

How do noise-cancelling headphones work?

Nowadays, the city is full of various environmental noises. To solve the noise problem, noise-reducing headphones that overcome the noise have come out on the market. Ordinary noise reduction headphones generally use physical noise reduction, and a certain anti-noise function can be achieved by using better earplugs and ear pads. Its principle is to block the ambient sound directly into the ear as much as possible, that is, use a specific material to isolate the external noise. These are all passive noise reduction. Passive noise-cancelling headphones can reduce 15-25 decibels under ideal conditions, but they cannot prevent low-frequency noise from slipping into the ears and cannot satisfy people who are more sensitive to sound or afraid of noise.


Therefore, to overcome the shortcomings of passive noise-cancelling headphones, active noise-cancelling headphones also came into being. The design of this kind of earphone is much more complicated. It is necessary to equip a microphone for receiving noise outside the earphone audio source line. After receiving the noise, the anti-noise program will send out the opposite audio according to the sound wave of the noise to offset it. Active noise-cancelling headphones can deal with most frequency bands of noise. Active noise reduction headphones are composed of a pickup (capturing environmental noise), a processing chip (analyzing noise), and a speaker (generating reverberating sound waves) to complete the entire noise reduction process. Some active noise-cancelling headphones are also equipped with a button. If users want to receive external sounds, they can turn off the anti-noise program by clicking the button instead of removing the entire pair of headphones.


In addition to being used to eliminate interference from external noise to work, active noise-cancelling headphones are better than traditional soundproof earmuffs. They were first used in high-noise operating environments, such as aviation, weeding, target shooting, shooting, etc. It is used as a sleep aid for people who are sensitive to noise. Nowadays, there are already a series of civilian, active noise-cancelling headphones on the market, which makes the application range of noise-cancelling headphones wider, and more and more people are also aware of this powerful headphone product.


Active noise reduction working mode:

  • The microphone collects noise signals;
  • The built-in chip algorithm performs arithmetic processing on the signal and parallels the signal to the music signal (the designer is required to perform acoustic analysis on the possible noise and noise, according to the frequency, phase and amplitude changes of the noise that may be transmitted to the ears, Build the same algorithm);
  • The horn emits music with noisy reverse sound waves (neutralizes external noise while playing music).

Classification and principle of active noise reduction:

  • Feed-forward active noise reduction

To put it simply, the microphone is exposed to noise and isolated from the speaker. The feed-forward design isolates the microphone from the earphone speaker unit (that is, the sound collection point of the microphone is designed on the surface of the earphone cavity) to ensure that the sound waves generated by the speaker have the least impact on the microphone. This design is the most direct method of noise collection. After the microphone collects the noise signal, it is transmitted to the chip for processing, and the reverse sound wave is emitted through the speaker to neutralize the noise.


  • Feedback active noise reduction

Place the microphone as close to the speaker as possible. The feedback type active noise reduction designs the noise collection microphone near the speaker. Compared with the feed-forward type, the noise collected by the feedback type is closer to the noise that can be heard by the human ear, but a major disadvantage of this design is the microphone. It is not possible to distinguish the difference between the sound and noise emitted by the speaker. If there is a sound similar to the noise in the music, it will also be recognized as noise and be processed, which will distort the music to a certain extent.


  • Combination of feed-forward and feedback

There are two microphones at the same time, one is isolated from the speaker, and the other is close to the speaker. This method combines the above two noise reduction designs and has two microphones. In addition to increasing the material cost, this design is also a big challenge for establishing the built-in noise reduction chip algorithms that allow urban travellers to adopt hybrid noise reduction technology.


All in all, the current active noise reduction technology has been developed for decades, and the technology has continued to mature. It is gradually extending from high-end applications to the civilian market, and the application environments are also diverse. The most fundamental thing is that compared with passive noise reduction materials, the processing mechanism of active noise reduction has more room for improvement. At present, our display is also focusing on the field of active noise reduction headphones, constantly exploring and improving active noise reduction technology and striving to make better headset products. Now the social environment we are facing is becoming more and more complex, and the environment in life is getting bigger and bigger. Popularizing noise-cancelling headphones and bringing them to the masses of consumers is also the original intention of the display.