Get rid of white noise in background?

Is there a way to get rid of a very soft white noise in the background of guitar or bass recordings? Its from the recording, which was not done in audacity, but I was hoping audacity might have some type of tool to get rid of it. thanks

Audacity’s noise reduction should help, (set the noise reduction as low as possible, typically around 10dB)

http://manual.audacityteam.org/index.php?title=Noise_Removal

http://www.youtube.com/watch?v=mlKX6p85R2M

In a bass recording you may also be able to cut back the high frequencies in Audacity’s equalizer, which would reduce the hiss without affecting the bass too much.