Noise Reduction Trick

[kozikowski]

It's pretty common to amplify noise before making it a profile in Noise Reduction. Is it common enough to burn it permanently into the effect?

Koz

[waxcylinder]

If you made this into a feature request I'd vote for it Koz.

WC

[bgravato]

I do not know the internal maths for the noise reduction effect, but in practical cases in which I've used the effect it was most effective doing that trick... without the trick the result of noise removal was very unsatisfactory...

So I'd say "why not?"
Sounds like a good idea...

[steve]

Is it common enough to burn it permanently into the effect?

Yes and it is already in Audacity 1.3.13 alpha.
The amount of "amplification" of the noise profile is set by the new "Sensitivity" slider. The default Sensitivity setting of 0 dB equates to the same as it is in Audacity 1.3.12 beta.
Also, the Attack/decay setting works now (if you'd not noticed, it doesn't do anything in Audacity 1.3.12)

Unfortunately there is still a minor bug in that two of the sliders (Sensitivity and Attack/decay) don't respond correctly to arrow keys or mouse wheel bug 227 I don't know if this is anything that Edgar or Bill could have a look at?

[kozikowski]

The amount of "amplification" of the noise profile is set by the new "Sensitivity" slider.

I don't know that I would have done it that way. The settings for this are fairly constrained. The sample needs to be bigger than it is now and at no time should it clip. In my book that should be Auto or Manual. [X] Auto (default) applies Amplify to -1. [X] Manual starting point for the slider is the old value.

Can you save a noise reduction correction? I broke up my hours-long lecture into four parts and need to correct all the parts the same way.

I thought about this some a little earlier. What happens to the tool if you apply Normalize instead of Amplify? What happens to the noise reduction if the sample is non-symmetrical compared to the show?

Can you listen to the rejection, a-la Sound Soap? Show me what I'm removing.

Koz

[steve]

The settings for this are fairly constrained.

It's enough.
The available range of the slider has been set according to the results from testing on a wide range of audio samples (I took part in the testing). The range was finally set with values greater (and smaller) than were required by any of the test samples. I feel fairly confident that the available range is greater than will be required for optimal noise reduction regardless of the source material. If someone want really extreme settings (for example as some kind of "special effect" rather than for noise reduction) then they can still resort to the manual method, though I can't think of any practical situation where this might apply.

The sample needs to be bigger than it is now...

You mean greater amplitude? In many cases an amplified noise sample will produce subjectively better results as more noise will be removed. However, this is at the expense of increased damage to the remaining audio. Settings higher than 0 dB gain will (always?) increase the damage to the remaining audio.
The sensitivity slider dB scale refers to the gain (amplification) amount, not an absolute dBFS level.

and at no time should it clip

I believe the noise sample is in 32 bit float format, so it will not clip unless it exceeds something like +1500 dB.

Can you save a noise reduction correction?

Currently no, although the noise profile is retained within an active Audacity session until the session is either closed, or the noise sample is overwritten with a new noise sample. That could be a feature request if you think that the usefulness outweighs the increased complexity.

Can you listen to the rejection, a-la Sound Soap? Show me what I'm removing.

Yes. You can select "Remove" or "Isolate".

[billw58]

Can you listen to the rejection, a-la Sound Soap? Show me what I'm removing.

Yes. You can select "Remove" or "Isolate".

But only in 1.3.13. I think Koz has an aversion to alpha software.

-- Bill

[bgravato]

I don't have aversion to alphas, but I usually have some "laziness" to anything that requires more than typing "apt-get install <whatever>" to install it (or dragging an icon from a .dmg to applications if i'm on mac )

[Edgar]

there is still a minor bug...I don't know if this is anything that Edgar or Bill could have a look at?

I am no longer doing a lot of programming of Audacity and not really keeping up with the forum. I have a vague recollection that this problem popped up in some other dialog and one of the Developers was able to fix it quite easily. I do not recall for sure but think the discussion was on the -devel list but I do not see anything with a quick search of Nabble.

I have not run a current alpha in months (I do grab the code and compile it every few weeks) but will take a quick look today.

[steve]

Good luck with it Edgar, and a happy Christmas.