Noise Reduction

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Noise Reduction

Permanent link to this post Posted by keejoh » Sat Nov 05, 2011 2:34 pm

I have just started using Audacity to convert some vinyl to MP3 files. I find I get a lot of hum/hiss come through from my hi fi equipment. Is there a way of filtering this out in Audacity.

Thanks
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Re: Noise Reduction

Permanent link to this post Posted by steve » Sat Nov 05, 2011 2:40 pm

Here are the instructions for using the Noise Removal effect: http://manual.audacityteam.org/man/Noise_Removal

There is also a more comprehensive guide to noise removal on the Audacity wiki that includes suggestions of other tools that may help. http://wiki.audacityteam.org/wiki/Noise_Removal

For Linux users there is a free program called "Gnome Wave Cleaner" which is a very advanced noise removal program that is capable of much better noise reduction than can be achieved with Audacity. Similar tools may be available for other operating systems.
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Re: Noise Reduction

Permanent link to this post Posted by littlemario » Fri Dec 09, 2011 8:24 pm

Hello everybody
It's my first message... I write here because my problem is about the same subject

I'm a videomaker but completely ignorant about the wide and complex world of audio and audacity...
I've just downloaded the 1.3.13 and in my ignorance I can recognize that a GREAT work was done and bow my head...

My problem is to clean a part of a speech that I recordered while I was a little bit far from the speaker, so... I used audacity as a real newbie, and... yes! I was able to improve the quality of this one minute clip ;) :geek:

...but I have to recognize that I've reached perhaps 20/30% (maximum!!) of the possible improvement, because even using the "prelistening" button, all the settings and all the passages that should be done... it's so far from my "01% competences" level :roll:
...and I've read Noise Removal and How Noise Removal Works...

So... I'm happy to use Audacity that is really great (!) but... I'd have a request too :oops:
there's anyone that could help me to have a real good result with this little clip?
I'd put his name in the credits of the video and obviously be sincerely grateful
Thanks
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Re: Noise Reduction

Permanent link to this post Posted by steve » Fri Dec 09, 2011 10:36 pm

littlemario wrote:anyone that could help me to have a real good result with this little clip?

Could you upload it somewhere and post a link so that we can hear it.
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Re: Noise Reduction

Permanent link to this post Posted by littlemario » Mon Dec 12, 2011 3:41 pm

steve wrote:
littlemario wrote:anyone that could help me to have a real good result with this little clip?

Could you upload it somewhere and post a link so that we can hear it.

Thank you so much for your interest Steve!
I tried to find another audio source but the situation is the same or even worse... but I was able to find another little talk part

Here's the speech I was talkig about
discorso prima parte.wav

I know that miracles are not so "easy"... but surely you can do better than me...

Many many many (n-times) thanks!
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Re: Noise Reduction

Permanent link to this post Posted by billw58 » Mon Dec 12, 2011 4:21 pm

The Noise Removal tool is meant to remove constant, unchanging noise such as hiss, hum or air conditioner noise. You have echo (from being too far from the speaker); wind noise (which varies in loudness and quality); random crowd noises and traffic noises. Noise Removal cannot effectively attack any of those. The best I was able to do was by taking the noise sample from 24.63 to 25.43 seconds, then applying noise reduction with a Noise Reduction setting of -12. This helps a little. Higher settings of the Noise Reduction slider begin to affect the quality of the voice, making it sound worse.

-- Bill
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Re: Noise Reduction

Permanent link to this post Posted by littlemario » Mon Dec 12, 2011 4:55 pm

Yes billw58, your analysis is more than correct... There's this echo and crowd noises and mostly at the end that wind... And I know that it will never be a clean audio :(
I'm just looking for something more "acceptable"

Now I'm trying to follow those settings but... -12 I suppose is for Sensibility; and I have to keep my other default setting?
...that is to say: Noise reduction 15 (it's only positive values) - Frequency reduction: 590 - Time 0,15

Anyway is it possible to improve tha voice sound? Maybe with a correct equalization and/or compression?
For the second I really dont' know anything, but for the eq i suppose i have to draw a "smile" (lower in the centre frequencies): is it correct?

Many thanks!
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Re: Noise Reduction

Permanent link to this post Posted by steve » Mon Dec 12, 2011 5:33 pm

littlemario wrote:Anyway is it possible to improve tha voice sound? Maybe with a correct equalization and/or compression?
For the second I really dont' know anything, but for the eq i suppose i have to draw a "smile" (lower in the centre frequencies): is it correct?

Yes Equalization can also help, but not a "smile" shape. The bass frequencies are quite prominent so they can be reduced a bit, and low frequency noise (below about 100 Hz) can be reduced dramatically. The high frequencies are quite lacking, so a little boost around 2 kHz can help to make the voice a bit clearer, but may also make the background noise more noticeable. I'd suggest starting with settings similar to this, then tweak it for best results.

eq.png
eq.png (45.22 KiB) Viewed 2253 times


After Equalization you will probably find that there are a few very high spikes in the waveform (caused by moments of "clipping" in the unprocessed waveform). To deal with these, first use the Amplify effect to bring the peaks within the normal 0 dB range, then use the Limiter effect (an optional plug-in available here).
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Re: Noise Reduction

Permanent link to this post Posted by billw58 » Tue Dec 13, 2011 4:24 am

littlemario wrote:Now I'm trying to follow those settings but... -12 I suppose is for Sensibility; and I have to keep my other default setting?
...that is to say: Noise reduction 15 (it's only positive values) - Frequency reduction: 590 - Time 0,15


Its the "Noise Reduction" slider I set to -12. The more noise reduction you ask for, the more likely you are to damage the audio you are trying to preserve.

I never set Sensitivity other than 0. Others may disagree.

-- Bill
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Re: Noise Reduction

Permanent link to this post Posted by steve » Tue Dec 13, 2011 5:58 pm

billw58 wrote:I never set Sensitivity other than 0. Others may disagree.

I usually leave the Sensitivity at 0. In most cases 0 is the optimum setting for Sensitivity. With some material raising the Sensitivity can help to remove more noise, but in most cases it will also increase the damage to the remaining audio.
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