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Making Sounds Louder/Suppressing Noises


Domi

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I know that it can be done post-recording, and even did it once looong time ago, but I can't remeber! I was wondering if someone could post a link, or post a few recipies for cleaning files from noise and making them louder :O I am using Audacity. Thank you in advance!

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I know that it can be done post-recording, and even did it once looong time ago, but I can't remeber! I was wondering if someone could post a link, or post a few recipies for cleaning files from noise and making them louder :O I am using Audacity. Thank you in advance!

 

Well, if the noise is not too serious, Audacity has a noise reduction plugin included, but it really cannot work miracles. This type of noise reduction algorithm works by taking a sample of the background noise (from a portion of the file which is silent except for the noise) and then using that frequency pattern as a filter for the file. The good news is, that it will in most cases remove all noise from the silent portions of the file, but the bad news is, that it will in most cases impart a clearly audible metallic tinge to the sound, along with high-frequency artifacts that can be heard as a "tinkle" in the background. If you want to try if this algorithm works in your case, here's how you use it:

 

1. Select a silent portion of the waveform (where there is nothing but background noise).

2. Select Effects -> Noise Removal.

3. Click Get Noise Profile.

4. Select the whole file.

5. Select Effects -> Noise Removal again.

6. Set the slider all the way to the Less end of the scale.

7. Click Remove Noise.

8. Listen to the clip; if enough noise is not removed, Undo and repeat from step 5, moving the slider one step to the right and listening to the result again.

 

This will probably remove most of the noise, but will also make the voice sound metallic and tinkly.

 

It is also possible to at###### background noise by chaining together an expander and a compressor and tweaking their settings suitably; this requires a program with realtime effects (Kristal Audio Engine is a good free alternative) and the appropriate plugins (Floorfish and Blockfish from Digitalfishphones are quite good free alternatives). Since the settings have to be tailored for each sound clip, and the whole process is very much about flying by the seat of your pants and using your ears, I really cannot give you step-by-step instructions. This method can give passable results in some cases, but often the "pumping" effect and variation in the noise levels are just as disturbing as the original background noise (just in a different way).

 

If the noise is disturbing only during the bits of silence in the recording (and sufficiently masked by the voice itself), a noise gate (such as Floorfish mentioned above) could also be enough.

 

Also creative use of equalisation can help to reduce background noise without too much disturbance, depending on the frequency and bandwidth of the noise. If you want more precise suggestions on what might work, a sample clip of the noisy recording would be helpful.

 

In my experience, however, the easiest solution by far is to eliminate noise already in the recording phase. After-the-fact nosie removal is very hard to do without producing artifacts.

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I have just tested the demo version of Redunoise, a new noise removal plugin from Voxengo, and I'm happy to report that at least in the case of uniform, non-oscillating background hiss, it is very significantly better than the native noise removal function of Audacity. It can lower the noise floor significantly without affecting voice quality to a noticeable degree.

 

Fortunately for us, the only limitation of the demo version (available at http://www.voxengo.com/product/redunoise/) is a few seconds of silence every 25 seconds. Since most voice clips are shorter than that (or should be, IMO), it can be used for them without hindrance.

 

Since the plugin is much more versatile and tweakable than the one in Audacity, it does take some fiddling around to figure out (there is a good manual on its home page), but for anyone who cannot for some reason eliminate background hiss at the recording phase, it is a godsend. Being a VST plugin it will need a VST capable host application like the free Kristal Audio Engine or Cubase, and its complexity also means that it can be somewhat CPU intensive on higher settings.

 

I do not claim to have figured out more than the basics, but if someone needs help in figuring it out, I can try to be of assistance. It can really help to get rid of problematic noise without introducing the tinkly and metallic sound that the Audacity one introduces to the voice.

 

BTW, Domi, did you manage to clean out the sound files?

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