NRR denoising index is the abbreviation of Neural Regeneration Research. The denoising value of ear plugs is most often represented by NRR, which is the noise attenuation level. Active noise reduction belongs to hardware noise reduction. The principle is to use the circuit to pick up the ambient sound around, and then convert it into an inverted sound signal and add it to the horn end. The sound presented to the human ear is the environmental noise + the inverted environmental noise. Another major noise reduction technology is software noise reduction, also known as CVC noise reduction, which comes with the chip. It only works when you make a phone call. With this technology, ambient noise can be attenuated and the other party can hear a clearer voice. At present, there are few TWS earphones that can achieve active noise reduction on the market. Due to the guidance of big brands, the industry has started to strengthen the research and development in this aspect, so this year active noise reduction will become a major advantage of the TWS bluetooth earphone selling point!