active noise reduction and passive noise reduction.
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 external noise through the noise reduction system to neutralize the noise, thereby achieving the effect of noise reduction. Active noise-canceling headphones have a noise-canceling 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 sound-insulating materials such as silicone earplugs to block external noise. Since the noise is not processed by the noise reduction circuit chip, it can only block high frequency noise, and the noise reduction effect on low frequency noise is not obvious.
The three noise reduction measures usually 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 frequency 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 broadcast 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 environmental 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.