You may need to try recording in a more quiet environment. Microphones will pick up anything and everything... even things you might not hear yourself while recording.
Or if you're talking about a bad signal, you need to be sure you have a good audio interface that provides good (as in quiet) microphone preamps and you need to be connecting your mic to your audio interface with a good, balanced XLR mic cable to get a clean signal.
A good book reference for recording with micrphones is:
* Getting Great Sounds: The Microphone Book -
http://digifreq.com/?MicrophoneBook Scott
--
Scott R. Garrigus -
http://garrigus.com * Author of the Cakewalk Sonar and Sony Sound Forge Power book series:
http://garrigus.com/?PowerBooks * Author of the Cakewalk Sonar ProAudioTutor video tutorial series:
http://garrigus.com/?ProAudioTutor * Publisher of the DigiFreq free music technology newsletter:
http://digifreq.com/?DigiFreq * Publisher of the NewTechReview free consumer technology newsletter:
http://newtechreview.com/?NewTechReview