“The active noise control (ANC) technology reduces noise by using antiphase sound to cancel the source of the sound that is creating noise. This is an effective method for countering most low-frequency sounds. However, there are many instances in which the problem actually lies with high-frequency sounds. This is the challenge that researchers are facing in using ANC technology for noise reduction of high-frequency sound waves.”

“Sound is a pressure wave, which consists of a compression phase and a rarefaction phase. A noise-cancellation speaker emits a sound wave with the same amplitude but with inverted phase (also known as antiphase) to the original sound.”

“The waves combine to form a new wave, in a process called interference , and effectively cancel each other out – an effect which is called phase cancellation .”