There are two types of ANC, which include: Feedfoward & Hybrid.

Feedfoward is a form of ANC which uses microphones on the outside of the headphone/earbuds to calculate the waveform. Although highly effective, as the microphones are located on the outside, they are sometimes susceptible to wind or physical interference.

Hybrid on the other hand is a far more advanced form of ANC. Hybrid ANC utilises micrphones positioned on the outside and inside of the headphones or earbuds, thus enabling the technology to listen to "itself" and make instant corrections to the opposite waveform, further increasing the ANC efficacy across all wavelengths.