Usage of Headphones have increased considerably with the arrival of Smart Phones and other portable devices. Many use the Noise Cancelling Headphones to listen to Music and other Audio. Do you know how do they cancel the Noise?
Process
The Noise Cancelling Headphones cancel out unwanted external sound (noise). They do this by creating a sound wave similar to the noise you want to get rid of. This sound wave which is 180 degree out-of-phase with the noise, opposes it and thus cancels out. Here we will have two sound waves – one at its peak level (Noise) and other at its lowest level (Correction Signal) – which are effectively cancelled. This process is known as “Destructive Interference”.
How it happens
There are two main components in achieving Noise Cancellation. A Microphone and a Noise Cancellation Circuitry. The Earcup will contain a Microphone to listen to the external sound (Noise). When a Noise is detected, the Microphone sends the sound signals to the Noise Cancellation Circuitry. The Frequency and Amplitude of the Incoming Sound Wave is detected by the Circuitry.
The Circuitry then generates an opposite, “Out-of-Phase” sound wave and feeds it back to the Speakers in the Headphone. This is mixed with the Sound Waves of the Music or Audio that you are listening to.
When the Noise and the Correction Signals combine, they get cancelled mutually, thus creating a Noiseless listening. This however does not affect the audio that you are listening to.
Noise Cancellation works well with lower frequencies, though it is not possible to cancel out the Noise hundred per cent.
