#antiphase

• Antiphase — A state or relationship between two periodic quantities (waves, oscillations, signals) of the same frequency, characterized by a phase difference of exactly 180 degrees (or π radians); phase opposition. In acoustic and electronics engineering, bringing waves into antiphase is the core principle used for active noise cancellation.
• Antiphase — Being in phase opposition (shifted by exactly 180 degrees) relative to another oscillatory signal, electromagnetic wave, or sound wave of the same frequency. In modern audio technology, antiphase signals are utilized for active noise cancellation.