How Active Noise Cancellation Actually Works: From Destructive Interference to Real-Time DSP
In 1936, a German physician and philosopher named Paul Lueg received U.S. Patent 2,043,416 for a concept that would take nearly 60 years to reach consumers. His invention: using sound to cancel sound. The patent described how to attenuate sinusoidal tones in ducts by phase-advancing the acoustic wave and canceling arbitrary sounds around a loudspeaker by inverting polarity. Lueg had discovered the fundamental principle of active noise control. He had no way to implement it. ...