I imagine it’s like the Active Noise Canceling (ANC) mode of headphones which will monitor background noise and then calculate the inverse sound wave and play that sound to you which in effect mostly cancels out the background noise (works better for certain frequencies than others). For a microphone they could do the same but instead of playing you the inverse sound, they could play it through the microphone for whomever is listening.
I imagine it’s like the Active Noise Canceling (ANC) mode of headphones which will monitor background noise and then calculate the inverse sound wave and play that sound to you which in effect mostly cancels out the background noise (works better for certain frequencies than others). For a microphone they could do the same but instead of playing you the inverse sound, they could play it through the microphone for whomever is listening.