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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 [url=http://www.lcdmo.com/jordanpascher.php]air jordan pas cher[/url] in your pocket.
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Passive headphones essentially utilize the muffling characteristics that are provided by circum- aural headphones. [url=http://www.lcdmo.com/jordanpascher.php]jordan pas cher[/url] It is designed like a cup with the rim surrounding the ear. The rim constitutes of high- density foam and sound [url=http://www.thehygienerevolution.com/barbour.php]barbour[/url] 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 [url=http://www.jordanpascherofficiel.com]air jordan[/url] is [url=http://www.jordanpascherofficiel.com]air jordan pas cher[/url] 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 [url=http://www.davidhabchy.com]barbour outlet[/url] 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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