[Newbie alert: I have been in this discipline for less than 2 weeks!]
Thanks for your kind assistance, Gale:
My goal is to become an expert in NR.
(1) First, as an interactive user (with Audacity, Audition, Sound Cleaner II, iZotope RX4 or whatever tool I can find out there - I gather that professionals have a veritable Swiss army knife of applications -or rather: arsenal, at their disposal.)
That would be a steeping stone to …
(2) Programmatically, writing my own functions, plugins, etc. [this is the real cool part, only possible with Audacity]
I have found the visual erasing technique (invented by Adobe Audition, cloned by RX-4, see image) invaluable, for Stage (1) above, specially for the type of NR (really noisy) in which I am interested.
I assume that those “brush operations”, Photoshop-style, have some sort of equivalent Audacity functions? I am guessing that they are under the “Effect” menu?
Let’s say that I am past the Audacity “Noise Reduction” menu item in which I provided a Noise Profile. Assume further that I have been veeeery careful not to overdo it and the dreaded “wine glass” is absent but undesirable noises are still present.
There is no “one size fits all” answer. It depends what sort of noise you are needing to remove. For example, if you need to remove sub-sonic rumble you would probably use a high pass filter (though usually best to apply that before noise reduction effects). If there were a constant high pitch whistle, then you may be able to deal with it using a notch filter. If there is heavy clipping noise, then you can forget about audio restoration - you can’t put back what’s not there. If there are clicks and crackles, then again it is likely to be better to deal with those first.
No real equivalent in 2.0.6 except for Notch Filter applied to all frequencies in a time selection.
In the next 2.1.0 release you will be able to make a rectangular spectral selection and use spectral edit tools in the Effect menu to filter that spectral selection. Freeform-shaped spectral selections may come later.