When used with voice recognition software, it is crucial for the microphone 
to pick up only the speaker's voice and reject unwanted noises from the
surrounding environment.  A microphone with a UNIDIRECTIONAL or CARDIOID 
polar pattern is ideal for this, as it will only pick up sound from in front, 
while rejecting sounds from the back and sides.  

OMNIDIRECTIONAL microphones perform poorly for voice recognition, as they pick
up sounds equally from all directions.  Environmental noise is picked up which
"confuses" the software.

Either a DYNAMIC or CONDENSER microphone can be used for voice recognition, 
so long as it is Unidirectional or Cardioid.  (A Condenser microphone will 
need a battery or a power pack to work with most sound cards.)

The microphone that Dragon supplies with Naturally Speaking is a Cardioid
Condenser microphone. 

To learn more about the different types of microphones on the market, see the
article "Mics - types of microphones".

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