What is so great about USB mics?  In the year 2000 USB microphones became available. These microphones provided us with another way to improve recognition accuracy. The USB microphones or the USB mic pod provides its own sound system outside of the computer. With the sound system outside the computer the input does not compete with the computer noise, this therefore results in better accuracy especially in notebook computers or computers that have marginal soundcards.  Most new desktop computers have pretty good sound recording capability. 

With NaturallySpeaking installed you can check your sound quality by selecting Tools, Accuracy Center then Check Your Audio Settings. Run the wizard, at the end of reading the second paragraph (Step 4 of 4) the wizard reveals a number for speech to noise ratio. If your number is 17 or higher the microphone you have is probably fine. If it is 16 or lower you might want to consider a USB microphone or mic pod.  A USB mic pod is a unit that provides a sound system and plugs into your USB port. You then plug your regular microphone into the USB pod which by passes the sound card inside the computer.