Noise is unwanted in recordings, in fact they do exist and should be removed. Noise in recordings can surely ruin the quality of the mix and decrease the professionalism of the work.
This post covers the noise removal procedure using Adobe Audition 1.5 recording software using Edit View (if you are doing multi-track, clicking those tracks in detail brings you to the edit view of the waveform per track)
Step 1:
Identify the portions of the recording where noise is the only signal. Looking below, I have planned to have at least 1 to 3 idle seconds before I start recording , the purpose is to have portions only for the noise.You can see below that the noise is being highlighted in the beginning portions.

You can hear the mp3 equivalent of this "noise + recorded guitar track":