The principle of ANC noise-cancelling headphones

As we all know, Bluetooth headsets are mainly divided into passive noise reduction and active noise reduction in terms of noise reduction. Most of the methods on the market are passive noise reduction. From 2022, it should be the market of active noise reduction, that is, the trend of ANC noise reduction headphones, so Bluetooth headset manufacturers will elaborate on the principle of ANC noise reduction headphones today, so that everyone can better understand ANC active noise reduction headphones.

Noise Cancelling Headphones

Active noise reduction can generally be subdivided into Feedforward ANC (feedforward active noise reduction), Feedback ANC (feedback active noise reduction) and Hybrid ANC (hybrid active noise reduction, which is actually feedforward plus feedback). Each of these methods can be divided into adaptive (adaptive) and non-adaptive (non-adaptive) ANC. Generally speaking, adaptive ANC can only be digital (digital) control. However, under non-adaptive ANC, it can be divided into analog (analog) and digital ANC. A long time ago, because the DSP chip was not powerful and did not support real-time complex calculations, etc., there were only analog ANC headphones on the market, that is, the calculated ANC controller was implemented with components such as capacitors, inductors, and resistors. Now with the rapid development of DSP chips, ANC controllers can be digitized. There are many advantages, such as the strength of ANC can be adjusted, etc. Some headphones, noise reduction capabilities can be controlled by the mobile phone APP. Currently on the market is basically the world of digital ANC headphones.

Active noise reduction principle:

Active noise-cancelling headphones are much more complicated than ordinary headphones. A noise-cancelling module needs to be built into the headphones. It contains a microphone to receive external noise, and then through the calculation of the internal circuit, the headphones can play music while adding and The sound waves of the outside noise “invert”, thereby canceling the outside noise.

Here we mainly talk about active noise reduction. Active noise reduction is divided into three types of noise reduction: feedforward noise reduction, feedback noise reduction, and feedforward and feedback combination. Feedforward and feedback noise reduction Feedforward noise reduction is to design the microphone on the outside of the headset away from the speaker, while feedback noise reduction is to design the microphone near the speaker. Feedforward noise reduction is easier to implement, while feedback noise reduction can collect noise information that is closer to what the human ear hears, but the microphone may be affected by the sound of the speaker, which requires higher algorithms.

At present, most of the relatively high-end noise-cancelling headphones combine passive noise-cancelling, feed-forward and feedback noise-cancelling designs, which have a very good effect on noise shielding and elimination.

Due to the complex structure and working principle of active noise-cancelling headphones, the price is generally much higher, and most of them are at a price of 1,000 yuan or more. However, the shortcomings of active noise reduction headphones are also obvious. Since the sound unit will emit additional sound waves to cancel the noise, there will still be differences in the sound quality performance, and the sound details will be lost.

However, with the development of Bluetooth headset manufacturers’ technology, the current active noise reduction headphones also have quite good sound quality performance, and their applicability is broader than passive noise reduction. Although this technology has been developed for decades, there is still a lot of room for improvement. Conditional friends suggest that it is better to choose active noise-cancelling headphones.