There are two kinds of noise reduction methods for headphones, active noise reduction and passive noise reduction.
The active noise reduction function is to neutralize the noise by generating reverse sound waves equal to the external noise through the noise reduction system, so as to achieve the effect of noise reduction. Active noise reduction earphones are equipped with noise reduction circuits to compete with external noise. Most of them adopt large head mounted design. Earplug cotton and earphone shell can be used to block external noise for the first round of sound insulation. At the same time, in order to have enough space to install active noise reduction circuits and power supplies.
Passive noise reduction earphones mainly form a closed space by surrounding the ears, or use sound insulation materials such as silicone earplugs to block external noise. Because the noise is not processed by the noise reduction circuit chip, it can only block the high-frequency noise, and the noise reduction effect on the low-frequency noise is not obvious.
The three noise reduction measures commonly used to reduce noise, namely, noise reduction at the sound source, noise reduction in the process of transmission and noise reduction at the human ear, are all passive. In order to actively eliminate noise, people invented the technology of "active silencing".
