How to remove only a particular noise mixed with the speech in the whole audio files without losing the quality of sound of speech.

[AL H]

I like to know the detail steps of removing a particular unwanted noise mixed with the speech in my audio.  The auto noise reduction functions did not help. Using this auto function also reduces the quality of sound and getting lower.  I just want to remove the paritcular noise only. 

I think I need to use  " Grab noise sample from selected area for Spectral Subtraction" and Spectral Subtraction based on Sample" 

Am I correct ?  I cannot find the help in the Help.

I already watched the basic noise removing video tutor. It did not help my issue.

2) I also like to know more advanced noise reduction tutor video that explains each functions of noise reduction menu.

[MakubX]

This video tutorial should help https://www.youtube.com/watch?v=be8h3WEAbyo

Normally, you'd:
Click the Cleanup button on the Effects tab toolbar
Select Noise reduction from the submenu
Select Multi-band Noise Gating.. from the Noise reduction submenu
Select the Remove Hum and Hiss preset
Click OK