When I first heard about USB headphones and microphones, I couldn't figure out why anyone would want one. After all, sound is analog. At some point the digital signal from the computer needs to be converted into an analog signal to drive the headphone. And the signal from the microphone is analog by nature--what can a USB interface do to help things?
The answer, I discovered, is reduced noise. A digital USB headset microphone eliminates most sources of hum and distortion. The insides of a computer are unfriendly to audio circuitry--it's hard for the microphone input on the motherboard to be noise free. By doing the analog-to-digital conversion outside the computer's case, and feeding a digital USB signal into it, noise is reduced.
I was a bit disappointed when I plugged in the Plantronics device--recommended by Microsoft for speech recognition--and Windows XP told me that the driver wasn't certified for XP. It didn't seem to affect the performance at all with one exception--the "mute" button on the microphone doesn't function on Windows XP! (Plantronics says they know about this.)
The headphone sounds good, though for about half the price of this unit you can get an old-fashioned analog headphone that sounds OK. And the microphone, while not exactly hi-fi, made crisp, noise-free recordings.
I tried this headset with Windows XP's built-in speech recognition software and found it to be much better than using an external microphone. It also served me will with a USB camera for videoconferencing with the home office (I frequently telecommute.)
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