ANC headphones report background noise with microphones and invert its period utilizing created-in electronics. Then they Enjoy the inverted/opposite sound back into your ears, which cancels out the background noises. Physicist Werner Meyer-Eppler had been influenced by Homer Dudley's 1948 creation of your Vocoder and started in 1951 to operate https://www.youtube.com/watch?v=EgVkq214BvY