Noise cancelling works primarily through a technology called Active Noise Cancellation (ANC), which uses microphones, electronics, and speakers to reduce unwanted ambient sounds.

How Noise Cancelling Works

• Microphone Detection: Noise cancelling headphones or devices have built-in microphones that continuously listen to the ambient sounds around you. These microphones pick up external noises such as the hum of an airplane engine or traffic noise

• Sound Wave Analysis: The device's internal electronics analyze the incoming sound waves to understand their frequency and amplitude

• Anti-Noise Generation: The system generates a sound wave that is the exact inverse (or opposite phase) of the detected ambient noise. This "anti-noise" wave has peaks where the original noise has troughs and vice versa

• Destructive Interference: When the anti-noise wave meets the original noise wave, they cancel each other out through a process called destructive interference, significantly reducing the perceived sound reaching your ear

• Real-Time Processing: This process happens almost instantaneously because electronic signal processing is much faster than sound traveling through air, allowing the anti-noise to effectively cancel the ambient noise before it reaches your ear

Types of Noise Cancellation

• Passive Noise Cancelling: This involves physically blocking sound using materials like thick ear pads or foam earplugs. It is effective mainly for higher-frequency sounds but less so for low-frequency noises like engine hum

• Active Noise Cancelling (ANC): Uses the microphone and anti-noise technology described above to cancel out low to medium frequency sounds, especially constant noises

• Feedforward ANC: Microphones are placed on the outside of the ear cups to detect noise before it reaches the ear. Works well for steady background noise but struggles with sudden sounds

• Feedback ANC: Microphones are placed inside the ear cups to monitor the sound actually reaching the ear, adapting better to varying sounds but less effective at high frequencies

• Hybrid ANC: Combines feedforward and feedback methods for optimal noise cancellation

Limitations

• Noise cancelling works best with constant, low to medium frequency sounds such as engine noise or air conditioning. It is less effective against sudden, sharp, or high-frequency sounds like human speech or glass breaking

• The process can slightly affect music quality because the headphones add the anti-noise signal on top of the audio

In summary, noise cancelling headphones use microphones to detect ambient noise and then produce sound waves that are the exact opposite of those noises to cancel them out, improving the listening experience by reducing unwanted background sounds