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Noise cancelling headphones are useful to block out noise in noisy environments like trains, buses, and public places.
The technical theory that is worked out is that this device copies the sound waves from outside and then they make these sound waves go out of phase. It can be also compared to that of swimming upstream. If a river’s downstream current is directly proportionate to your upstream swimming strength, then you stay still.
In this case, the device stays quiet!
There are two models of noise cancelling headphones. Over-the -head headphones are a little larger and less compact but the Earbud headphones are compact and can be carried around in your pocket.
There are two types of headphones designed to reduce the interference of the noise that is created in the background. They are the passive noise canceling headphones and the active noise cancelling headphones. Passive noise cancelling headphones work on the theory of muffling the external noise or sound to lessen the interference with music or recorded speech.
Active noise cancelling headphones on the other hand, electronically decrease the external sound and produce a quiet and calm listening environment.
Passive headphones essentially utilize the muffling characteristics that are provided by circum- aural headphones. It is designed like a cup with the rim surrounding the ear. The rim constitutes of high- density foam and sound dampening material. It is soft and doesn’t hurt the ears and it creates an acoustic seal that has the capacity to block 20 decibels of noise.
Active noise cancelling headphones are a more advanced version and have the potential to reduce 20 decibels more noise reduction than the passive model. It uses the phase cancelling technology in its working. This is the main key feature of this model. It works by using a microphone to pick out the external noise which the circum- aural cushions are unable to prevent or block out.
The frequency and the intensity of the external noise are analyzed by the phase canceling circuit and it generates a mirror image of the noise. The noise created is 180 degrees out of phase.
The speaker of the headphones plays the anti-noise along with the music or recorded speech. The artificially generated anti-noise is exactly the opposite of the external noise that has entered the device and so when the two noises meet they cancel out each other. The end result is that the volume of the external noise becomes extinct and the audio you are listening to becomes very clear and audible.
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