Active noise cancellation

Different types of active noise cancellation techniques

a) The feed forward noise cancellation

 In a feed forward set up the microphones is placed outside the ear cup so these mic monitors the external noise and active noise cancellation circuits invert the noise into the anti noise and then it is mixed with the audio playback to create the noise cancellation now in this techniques has the mic picks up the noise early on it has a more time to respond and generate the anti noise and because of this it is good for the high frequency noise reduction.

b)The feedback-end noise cancellation

 In this type of noise cancellation technique the microphone is fitted inside the ear cup itself and as it is in front of the speaker it hear the resulting signal in exactly the same way the user does and because of that it can add up the variation in the noise easily. This feedback type of anti noise cancellation can only cancel the low frequency noise so to enhance the frequency range of the noise cancellation hybrid systems are used which combines both feed forward and feedback system.

c) The hybrid noise cancellation

In this techniques the microphones are placed inside as well as outside the ear cup and as it combines both feed forward and the feedback system the frequency range of the noise cancellation will also increase but at the same time these headphones are b quite expensive and bulky and usually they are only preferred for the specific applications.