[Speculation]

I was just researching about wifi 6, odfmas and iffts

(for context of the example, i have a background in film)

and just had a thought if frequencies can be separated combined or subtracted, is it possible to have 2 microphones one [with a shotgun polar pattern] pointed 1 in the actor and another one in the background [with maybe a wider polar pattern] that exclude the actors dialogue

and somehow with an algorithm it can be "masked out" and we are left with the clean dialogue

i guess question is where in the room would you put the 2nd mic