1.2.6 noise removal superior to 1.3.6 ??

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Re: 1.2.6 noise removal superior to 1.3.6 ??

Permanent link to this post Posted by steve » Mon Jul 19, 2010 3:28 pm

Comparisons between the Audacity Noise Reduction effect and ReaFir are, I think, only relevant to a point. While they apply similar technologies, the design goals are somewhat different. ReaFir aims to be a versatile FFT/dynamics processing tool, whereas Audacity Noise Reduction aims to be a simple to use Noise Reduction tool.

AEN007 wrote:2) Users can move the REAfir waveform up or down
which I guess is similar to the AudNR Noise reduction (dB) slider?

I think that is more like the new "Sensitivity" slider control.

AEN007 wrote:3) REAfir has an FFT level option. It seems that the higher the FFT level -
the more precise the noise waveform. I suppose the AudNR attack/delay slider
functions like the REAfir FFT level?

If you mean the FFT "size" parameter in ReaFir, then that does create a similar effect to the Attack/Decay control, but only as a side effect of the FFT size rather than being an independent control. I'm not totally sure here (you would need to check the Audacity code for a definitive answer), but I think that the Audacity Noise Reduction uses a fixed FFT size and the Attack/Decay settings operate directly on the gating function.

AEN007 wrote:4) I'm not sure what the REAfir equivalent of the AudNR Frequency smoothing is ...

I don't think it has one.
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Re: 1.2.6 noise removal superior to 1.3.6 ??

Permanent link to this post Posted by Gale Andrews » Tue Jul 20, 2010 2:22 am

stevethefiddle wrote:Comparisons between the Audacity Noise Reduction effect and ReaFir are, I think, only relevant to a point.

+1. However ReaFir seems to use spectral subtraction and I know Marco has tried that out with some success. I've got a bit lost in the detail of whether the latest patch with capture of Signal Profile (i.e. in the Windows Unicode Nightly Build) includes that or not. Perhaps he can clarify if no-one else knows.

AEN007 wrote:There is not one question in my previous post about REAfir

I'm afraid "I'm not sure what the REAfir equivalent of the AudNR Frequency smoothing is" looked like one to me. :)

It's highly unlikely ReaFir will work in Audacity in the short or medium term. So your help in providing samples that noise remove much better in ReaFir than in Audacity would be much more productive in improving Audacity's noise removal. ;)




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Re: 1.2.6 noise removal superior to 1.3.6 ??

Permanent link to this post Posted by Marco Diego » Wed Jul 21, 2010 7:51 am

AFAIK ReaFir is more similar to the current AudNR than spectral subtraction. I've never used ReaFir myself but, judging from what I saw (on youtube), it behaves like a multispectral noise gate (just like current AudNR).

Implement Reafir in AudNR is (AFAICS) almost as simple as using an EQ-Curve instead of the noise sample.
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Re: 1.2.6 noise removal superior to 1.3.6 ??

Permanent link to this post Posted by steve » Wed Jul 21, 2010 5:41 pm

Marco Diego wrote:AFAIK ReaFir is more similar to the current AudNR than spectral subtraction.

I think it can do either, depending on which mode you are using: http://www.cockos.com/wiki/index.php/Re ... aFIR_Modes
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Re: 1.2.6 noise removal superior to 1.3.6 ??

Permanent link to this post Posted by AEN007 » Fri Sep 10, 2010 10:05 am

10September2010
Greetings.

Gale Andrews wrote:
AEN007 wrote:There is not one question in my previous post about REAfir
I'm afraid "I'm not sure what the REAfir equivalent of the AudNR Frequency smoothing is" looked like one to me. :)
My posting was/is about understanding what AudNR does -
perhaps by using the visual examples that REAfir can provide. Thanks for the link in any case.

Gale Andrews wrote:It's highly unlikely ReaFir will work in Audacity in the short or medium term. So your help in providing samples that noise remove much better in ReaFir than in Audacity would be much more productive in improving Audacity's noise removal. ;)Gale
I have (once again) started working on my mp3/CD audio collection instead of my avi/MPEG/video collection. More than once I have experienced that REAfir removed noice from a CD rip better than AudNR - which would leave (or create) squeaky/scratchy "artifacts". AudNR worked as well (or better) than REAfir on video soundtracks. I don't know how or why this audio/video difference should exist???

stevethefiddle wrote:
AEN007 wrote:2) Users can move the REAfir waveform up or down
which I guess is similar to the AudNR Noise reduction (dB) slider?

I think that is more like the new "Sensitivity" slider control.
I don't "see" how that can be.
It seems to me that the AudNR dB slider is exactly like moving the REAfir waveform up or down ...

stevethefiddle wrote:
AEN007 wrote:3) REAfir has an FFT level option. It seems that the higher the FFT level - the more precise the noise waveform. I suppose the AudNR attack/delay slider
functions like the REAfir FFT level?
but I think that the Audacity Noise Reduction uses a fixed FFT size and the Attack/Decay settings operate directly on the gating function.

Does anyone know or could anyone find out what FFT level AudNR uses?
I use the 16384 (2nd highest) setting (in REAfir) for best results.

stevethefiddle wrote:
AEN007 wrote:4) I'm not sure what the REAfir equivalent of the AudNR Frequency smoothing is ...
I don't think it has one.
It is still now clear to me exactly what the AudNR options/settings do. I can clearly see/understand what the REAfir settings do.

My procedure for using REAfir in Audacity uses the Audacity PREVIEW option - which I guess is what causes REAfir in Audacity to take at least as long as the audio track to do the noise removal.
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Re: 1.2.6 noise removal superior to 1.3.6 ??

Permanent link to this post Posted by kozikowski » Sat Sep 11, 2010 6:52 am

Please note that if you're still trying to remove tape, or any kind of hiss, you can't really do that. "Hiss" is constructed of most if not all audible frequencies in a random fashion. If you successfully got rid of it, there would be no music left. Every musical note would be represented as some component of the hiss.

So the trick is to try and figure out which parts of the show are valuable and which ones aren't and straight noise sampling and subtraction is not going to do it. Worse, if you do get a particular technique to work on one show, it may very well not work on a different kind of show. I bet the NR in 1.3 which can have problems with music, works very well with spoken voice. I bet one of the rules is this: If the signal rises above the average of the hiss, it must be valuable and the suppression must be reduced. The rest of the adjustments have to do with how accurately the beginning and ending of a spoken word is selected.

Dolby Noise Reduction has been doing a similar trick in hardware for years. The presence of sound masks noise.

The particular NR software in 1.2 had no, in my estimation, adjustment range between space alien sound and no affect at all. I had to white knuckle the mouse to get any sort of useful work with the adjustment just up from dead zero. I thought it was broken for a long time.

I don't know how to get around this hiss thing. The software is already doing on-the-fly spectrum analysis and comparing the energy blobs to generate notch filters. 1.3 tries to add level contouring to avoid strange voices and pumping. What's left?

You run the risk of patching the show in such a way that it sounds OK, but doesn't sound like the original recording. That's why I've been using Steve's Noise Gate gently and I may not need to mess with the Noise Reduction.

Of course, if the hiss is loud enough, you have no choice.

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Re: 1.2.6 noise removal superior to 1.3.6 ??

Permanent link to this post Posted by AEN007 » Mon Sep 13, 2010 7:18 pm

kozikowski wrote:Please note that if you're still trying to remove tape, or any kind of hiss, you can't really do that. "Hiss" is constructed of most if not all audible frequencies in a random fashion. If you successfully got rid of it, there would be no music left. Every musical note would be represented as some component of the hiss.

Yeah, I've already contemplated that noise removal must remove some of the actual audio frequencies as well,
but nonetheless, this summer AudNR removed "noise/hiss" very well from my VHS»mpeg dubs.
I also process many Grateful Dead concerts - some audience some soundboard source.
Either might have originally been captured to analog tape; yet (often) REAfir (and sometimes) AudNR remove the "noise/hiss" without leaving any noticeable side effects.

My routine is more complicated because I like to use NCH WavPad (v3.02) Automatic Gain Control as the final step.
What seems like successful noise removal when NR is done before AGC might not sound as good after AGC.
It seems to me that doing NR before AGC is better than doing NR after AGC.
I have to apply NR to a sample (in Audacity); save; then run the AGC and listen ...
I like my files encoded at the maximum possible volume that does not create any distortion/clipping ...
I find most audio that I do needs bass boost and AGC and maybe noise removal.
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Re: 1.2.6 noise removal superior to 1.3.6 ??

Permanent link to this post Posted by kozikowski » Wed Sep 15, 2010 5:59 am

If you AGC first, then the NR has a constantly moving target. Not desirable.

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Re: 1.2.6 noise removal superior to 1.3.6 ??

Permanent link to this post Posted by AEN007 » Fri Dec 10, 2010 12:56 pm

10December2010

Any CD of Dark Side of the Moon should make a good sample for testing noise removal. I heard a radio interview (decades ago) with Roger Waters (who was trained not to spit on the fan). RW said just before PF was ready to release DSotM, Dolby came on the market; so PF ran the final product through one more time to add Dolby (which RW laughingly acknowledges - is NOT the way to do it.) DSotM was released saying "featuring Dolby NR" - but was not recorded using Dolby NR. The "noise" is impossible to miss - especially after applying automatic gain control. Finding a noise sample is a challenge.
As stated previously in this thread, it is better to do NR before AGC; but in some cases (as with DSotM), the noise (seemingly) has to be removed AFTER AGC ... I found that REAfir did better that Audacity NR (as almost always seems to happen with CD audio - as stated previously)
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Re: 1.2.6 noise removal superior to 1.3.6 ??

Permanent link to this post Posted by AEN007 » Fri Dec 17, 2010 4:20 pm

17December2010
Today I found here»
http://wiki.audacityteam.org/wiki/Downl ... t_Plug-ins
the Nyquist Broadcast Limiter II (RFT-Limiter-II.ny) -
which seems like AGC for Audacity.
Per the instructions here»
http://manual.audacityteam.org/index.ph ... ffect_Menu
I put the RFT-Limiter-II.ny file in the plugins folder
but Audacity does not seem to recognize the plugin.
Any helpful replies/insights appreciated.
Thank you.
Regards,
AEN
Æ
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