ANC headphones history background sounds with microphones and invert its phase making use of designed-in electronics. Then they Perform the inverted/opposite sound back into your ears, which cancels out the background noises. Physicist Werner Meyer-Eppler were impressed by Homer Dudley's 1948 invention of your Vocoder and started in 1951 to https://www.youtube.com/watch?v=7xCWDHDo9ZY