Active noise canceling: this is how it works

Active Noise Canceling (ANC) is a technology used to suppress background noise such as engine noise in an airplane. It is now increasingly found in headphones. We explain how ANC works.

Active noise canceling - what is it?

Active noise canceling describes the attempt to use noise waves to compensate for unwanted noise.

• Every sound creates sound waves that reach the ear of the listener through the air. However, not all sounds are pleasant and desirable: Airplane and train passengers are disturbed by the engine noise or the conversations of their fellow travelers.
• These noises are also perceived via sound waves. A so-called anti-sound is generated in order to extinguish these sound waves or to compensate them as best as possible. This is similar in amplitude and frequency to unwanted sound, but has an opposite polarity.
• The original sound waves are thus canceled by the principle of destructive interference. A third wave with the amplitude 0 arises - it is no longer perceptible.

How is active noise canceling implemented in modern headphones?

Headphones with active noise cancellation work in theory in the same way, but even the modern models cannot cancel out all the sounds.

• ANC headphones have a microphone that picks up sound from outside. A computer inside the headphones or in the cable processes the noise.
• The computer then emits sound waves through the loudspeakers, which ideally completely cancel out the background noise.
• The technology is still in the development phase. So far, noise can not be completely eliminated. So far, ANC has worked best with consistent sounds such as engine noise in an airplane.
• However, short and uneven sounds such as voices or brake squeals reach the wearer's ear almost undamped.
• Depending on the design of the headphones, in-ear, on-ear and over-ear headphones, this can have a greater impact.