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[Audacity-help] crackle removal

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[Audacity-help] crackle removal

John Rinehart
I have been editing recordings with audacity for about a year now but cannot figure out how to remove crackle noise from my tracks.  Some of this comes from old recordings, but some crackle noises appear as a result of "punch-in" editing.  Do you have a crackle removal tool for audacity available?
 
John

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Re: [Audacity-help] crackle removal

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    | From John Rinehart
    | Thu, 18 Jan 2007 11:37:57 -0500
    | Subject: [Audacity-help] crackle removal
    | I have been editing recordings with audacity for about a year now
    | but cannot figure out how to remove crackle noise from my tracks.
    | Some of this comes from old recordings, but some crackle noises appear
    | as a result of "punch-in" editing.  Do you have a crackle removal tool for
    | audacity available?

If you are "punching-in" areas of track the better solution is to trim the selection
you want to paste in to a safely joinable length before pasting it, using Edit >  
Find Zero Crossings. Or you can cross-fade the joints if you have the audio on
separate tracks in the Audacity screen.  

Regarding crackle you could try the Noise Removal tool under the Effect menu
if the noise is identical in the places where it occurs, and if you can find an
area of track which has only this crackle which you can then define as Audacity's
Noise Profile of the noise you want removed. Instructions for using Noise Removal
are pasted underneath this message. There is also a Click Removal effect for
removing clicks and pops, which works on the basis of detecting abrupt variations
in the volume of the track such as a loud vinyl pop would cause. Instructions
for Click Removal are also underneath.

Audacity does not currently have any very effective way for removing inconsistent
crackle or distortion noises that are typically heard only on higher volume signals
(on say an off-tune radio recording, or a worn or badly cut LP). I personally (on
Windows) use Goldwave's Noise Reduction filter for this, which is able to remove
this type of noise which falls between that of a constant background crackle, hum
or roar and a discrete pop or click.


Gale Andrews


*****************************************************************

** Noise Removal **

This effect is ideal for removing constant background noise such as fans,
tape noise or hums. It will not work very well for removing talking or music
in the background.

Removing noise is a two-step process. In the first step, you select a portion
of your sound which contains all noise and no signal, in other words, select
the part that's silent except for the noise. Usually this will be at the start or
end of the track, but if the track has no lead-in or lead-out, try zooming in
to hit a precise spot between a note or word. You select the part of the
track that is just noise by clicking in the track and dragging a selection out
with your mouse or with the arrow keys on your keyboard. Then choose
Noise Removal... from the Effect menu and click "Get Profile". Audacity
learns from this selection what the noise sounds like, so it knows what to
filter out later.

Then, select the audio from which you want the noise removed. If you want
to remove the noise from the whole track, select all of it by clicking in the
Track Panel where the Mute/Solo buttons are. Then choose Noise Removal
again. This time, click the "Remove Noise" button. It may take a few seconds
or longer depending on how much track you selected.

Most noise removal takes part of the recording away with the noise and
adds or exposes artefacts in the recording.  If not enough noise was
removed, or too much of the recording was removed along with the noise,
you can Undo (from the Edit menu) and try Noise Removal again with a
different noise removal level on the slider. You don't have to get a new
Noise Profile again if you think the first one was fine. However if the
problem is that too much of the music has been removed along with the
noise, you can also try try going back to the selection chosen for the Noise
Profile and reducing its amplification (Effect > Amplify). Then use this as
a new Noise Profile. Sometimes running the filter a second time using a
Noise Profile that is a deamplified section of track can give a good result.

It may still be impossible to get a satisfactory result when the noise
is very loud, when the noise is variable, or when the music or speech
is not much louder than the noise.

** Click Removal **

This effect is designed to remove individual clicks on recordings from vinyl
records without damaging the rest of the audio. First of all, select the
audio to which you want to apply click removal. You can choose how
sensitive the click detection is, and what the maximum length of a click is.

Sometimes an even better result can be obtained by zooming in to sample
level and silencing the click (Edit > Silence). The click will be visible as a
"spike" in the waveform. Most clicks up to 5 milliseconds long can be
silenced in this way without leaving an audible gap in the sound. If the click
is too wide to safely silence it, you can try analysing the area with Analyze >
Plot Spectrum to see if any spikes are concentrated in particular frequencies
and then use the FFT filter under the Effect Menu to reduce the volume of
those frequencies. You can do this more precisely with the Nyquist Notch
Filter:
http://www.shellworld.net/~davidsky/notch.zip

To install new plugins, unzip them into the Plug-Ins folder inside the Audacity
installation folder. On Windows computers, this is usually under "Program Files."
On Mac OS X, it is usually under "Applications." The plugins will be available
after restarting Audacity.

Noise from 78 rpm shellac records is often a combination of various noises like
roar, swish, crackle as well as individual clicks. Prominent clicks in 78 rpm records
can be taken out with click removal or direct silencing. However roar, swish and
fast crackle is better dealt with as noise removal. If it's possible to find sections
which have just these individual noise components, then treat these individually
by getting Noise Profiles and running Noise Removal for each. Compressing the
dynamic range can also help with 78 rpm noise (Effect > Compressor).

Audacity 1.3.2 also has a Repair effect for sections of badly damaged audio up to
128 samples in length.

IMPORTANT: If you are going to run click removal on all or most of the track, do it
before running noise removal, not afterwards.


 


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Re: [Audacity-help] crackle removal

John Rinehart
Can you explain how to use this Find Zero Crossings tool?

John Rinehart


----- Original Message -----
From: <[hidden email]>
To: "John Rinehart" <[hidden email]>
Cc: <[hidden email]>
Sent: Thursday, January 18, 2007 1:00 PM
Subject: Re: [Audacity-help] crackle removal


>
>    | From John Rinehart
>    | Thu, 18 Jan 2007 11:37:57 -0500
>    | Subject: [Audacity-help] crackle removal
>    | I have been editing recordings with audacity for about a year now
>    | but cannot figure out how to remove crackle noise from my tracks.
>    | Some of this comes from old recordings, but some crackle noises
> appear
>    | as a result of "punch-in" editing.  Do you have a crackle removal
> tool for
>    | audacity available?
>
> If you are "punching-in" areas of track the better solution is to trim the
> selection
> you want to paste in to a safely joinable length before pasting it, using
> Edit >
> Find Zero Crossings. Or you can cross-fade the joints if you have the
> audio on
> separate tracks in the Audacity screen.
>
> Regarding crackle you could try the Noise Removal tool under the Effect
> menu
> if the noise is identical in the places where it occurs, and if you can
> find an
> area of track which has only this crackle which you can then define as
> Audacity's
> Noise Profile of the noise you want removed. Instructions for using Noise
> Removal
> are pasted underneath this message. There is also a Click Removal effect
> for
> removing clicks and pops, which works on the basis of detecting abrupt
> variations
> in the volume of the track such as a loud vinyl pop would cause.
> Instructions
> for Click Removal are also underneath.
>
> Audacity does not currently have any very effective way for removing
> inconsistent
> crackle or distortion noises that are typically heard only on higher
> volume signals
> (on say an off-tune radio recording, or a worn or badly cut LP). I
> personally (on
> Windows) use Goldwave's Noise Reduction filter for this, which is able to
> remove
> this type of noise which falls between that of a constant background
> crackle, hum
> or roar and a discrete pop or click.
>
>
> Gale Andrews
>
>
> *****************************************************************
>
> ** Noise Removal **
>
> This effect is ideal for removing constant background noise such as fans,
> tape noise or hums. It will not work very well for removing talking or
> music
> in the background.
>
> Removing noise is a two-step process. In the first step, you select a
> portion
> of your sound which contains all noise and no signal, in other words,
> select
> the part that's silent except for the noise. Usually this will be at the
> start or
> end of the track, but if the track has no lead-in or lead-out, try zooming
> in
> to hit a precise spot between a note or word. You select the part of the
> track that is just noise by clicking in the track and dragging a selection
> out
> with your mouse or with the arrow keys on your keyboard. Then choose
> Noise Removal... from the Effect menu and click "Get Profile". Audacity
> learns from this selection what the noise sounds like, so it knows what to
> filter out later.
>
> Then, select the audio from which you want the noise removed. If you want
> to remove the noise from the whole track, select all of it by clicking in
> the
> Track Panel where the Mute/Solo buttons are. Then choose Noise Removal
> again. This time, click the "Remove Noise" button. It may take a few
> seconds
> or longer depending on how much track you selected.
>
> Most noise removal takes part of the recording away with the noise and
> adds or exposes artefacts in the recording.  If not enough noise was
> removed, or too much of the recording was removed along with the noise,
> you can Undo (from the Edit menu) and try Noise Removal again with a
> different noise removal level on the slider. You don't have to get a new
> Noise Profile again if you think the first one was fine. However if the
> problem is that too much of the music has been removed along with the
> noise, you can also try try going back to the selection chosen for the
> Noise
> Profile and reducing its amplification (Effect > Amplify). Then use this
> as
> a new Noise Profile. Sometimes running the filter a second time using a
> Noise Profile that is a deamplified section of track can give a good
> result.
>
> It may still be impossible to get a satisfactory result when the noise
> is very loud, when the noise is variable, or when the music or speech
> is not much louder than the noise.
>
> ** Click Removal **
>
> This effect is designed to remove individual clicks on recordings from
> vinyl
> records without damaging the rest of the audio. First of all, select the
> audio to which you want to apply click removal. You can choose how
> sensitive the click detection is, and what the maximum length of a click
> is.
>
> Sometimes an even better result can be obtained by zooming in to sample
> level and silencing the click (Edit > Silence). The click will be visible
> as a
> "spike" in the waveform. Most clicks up to 5 milliseconds long can be
> silenced in this way without leaving an audible gap in the sound. If the
> click
> is too wide to safely silence it, you can try analysing the area with
> Analyze >
> Plot Spectrum to see if any spikes are concentrated in particular
> frequencies
> and then use the FFT filter under the Effect Menu to reduce the volume of
> those frequencies. You can do this more precisely with the Nyquist Notch
> Filter:
> http://www.shellworld.net/~davidsky/notch.zip
>
> To install new plugins, unzip them into the Plug-Ins folder inside the
> Audacity
> installation folder. On Windows computers, this is usually under "Program
> Files."
> On Mac OS X, it is usually under "Applications." The plugins will be
> available
> after restarting Audacity.
>
> Noise from 78 rpm shellac records is often a combination of various noises
> like
> roar, swish, crackle as well as individual clicks. Prominent clicks in 78
> rpm records
> can be taken out with click removal or direct silencing. However roar,
> swish and
> fast crackle is better dealt with as noise removal. If it's possible to
> find sections
> which have just these individual noise components, then treat these
> individually
> by getting Noise Profiles and running Noise Removal for each. Compressing
> the
> dynamic range can also help with 78 rpm noise (Effect > Compressor).
>
> Audacity 1.3.2 also has a Repair effect for sections of badly damaged
> audio up to
> 128 samples in length.
>
> IMPORTANT: If you are going to run click removal on all or most of the
> track, do it
> before running noise removal, not afterwards.
>
>
>
>
>
> Outbound message virus free.
> Tested on: 1/18/2007 6:00:48 PM
>
>
>
>



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Re: [Audacity-help] crackle removal

audacity-help mailing list

    | From John Rinehart
    | Thu, 18 Jan 2007 14:55:07 -0500
    | Subject: [Audacity-help] crackle removal
    | Can you explain how to use this Find Zero Crossings tool?

It is not a tool but simply a command under the Edit menu, so you use this
command as you would others under the Edit menu, by first selecting the
track you want to apply the command to, then clicking the appropriate command.  

So select the track you want to paste in, and just click Edit > Find Zero Crossings
which will adjust the selection edges slightly to the nearest point where the audio
waveform passes through zero (i.e. appears on a positive-slope zero crossing).
Alternatively select the track and type the hotkey for Find Zero Crossings (Z by
default, but you can change this on the Keyboard tab of Preferences).

You won't see anything happening to the selection area unless you are zoomed a
long way in, but if you look at the Status Bar you will see that the area of the
selection has been very slightly changed.

If you cannot see Noise Removal or Click Removal in the Effect menu, please
upgrade to Audacity 1.2.6 or 1.3.2.


Gale Andrews






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Tested on: 1/18/2007 8:25:06 PM




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Re: [Audacity-help] crackle removal

John Rinehart
Another question : how do I amplify just one side/channel?  I have some old
recordings (these are all 1-track recordings) where for some reason the left
channel is much louder than the right.  I'd like to be able to even them
out.  Thanks,

John

----- Original Message -----
From: <[hidden email]>
To: "John Rinehart" <[hidden email]>
Cc: <[hidden email]>
Sent: Thursday, January 18, 2007 3:25 PM
Subject: Re: [Audacity-help] crackle removal


>
>    | From John Rinehart
>    | Thu, 18 Jan 2007 14:55:07 -0500
>    | Subject: [Audacity-help] crackle removal
>    | Can you explain how to use this Find Zero Crossings tool?
>
> It is not a tool but simply a command under the Edit menu, so you use this
> command as you would others under the Edit menu, by first selecting the
> track you want to apply the command to, then clicking the appropriate
> command.
>
> So select the track you want to paste in, and just click Edit > Find Zero
> Crossings
> which will adjust the selection edges slightly to the nearest point where
> the audio
> waveform passes through zero (i.e. appears on a positive-slope zero
> crossing).
> Alternatively select the track and type the hotkey for Find Zero Crossings
> (Z by
> default, but you can change this on the Keyboard tab of Preferences).
>
> You won't see anything happening to the selection area unless you are
> zoomed a
> long way in, but if you look at the Status Bar you will see that the area
> of the
> selection has been very slightly changed.
>
> If you cannot see Noise Removal or Click Removal in the Effect menu,
> please
> upgrade to Audacity 1.2.6 or 1.3.2.
>
>
> Gale Andrews
>
>
>
>
>
>
> Outbound message virus free.
> Tested on: 1/18/2007 8:25:06 PM
>
>
>
>



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Re: [Audacity-help] crackle removal

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    | From John Rinehart
    | Thu, 18 Jan 2007 15:46:27 -0500
    | Subject: [Audacity-help] crackle removal
    | how do I amplify just one side/channel?  I have some old
    | recordings (these are all 1-track recordings) where for some reason the left
    | channel is much louder than the right.  I'd like to be able to even them
    | out.

Are you recording these tracks into Audacity e.g. from a tape recorder? If so,
and the recordings are mono, why not record them in mono by making recording
channels = "1 (mono)" on the Audio I/O tab of Preferences? Also you can always
(if your Sound device supports it) adjust the balance of stereo recordings for the
source you're recording from (e.g. line-in) in the system mixer. On Windows this
would be the Audio tab of Sounds and Audio Devices in the Control Panel. Also
your recording source may have a balance control which may help if you are
connecting to its headphones output.    

If you do have pre-existing stereo files where one channel is weak, then click on
the downward-pointing arrow in the Track Panel (where the Mute/Solo buttons are)
then click "Split Stereo Track". You will now be able to amplify the volume of the
left and right channels independently, by selecting each channel in turn and then
choosing Amplify under the Edit menu. Audacity will offer you the amplification
needed for each track to scale it up to -0 dB (the highest possible amplification
without distortion), but you can choose another level if you wish.    

If you use the Normalize effect instead of Amplify, you don't need to split the
stereo track - this effect will normalise both channels to -3 dB automatically, but
in 1.2.6 you cannot choose a different normalisation level, whereas in the Beta
1.3.2 version, you can.
.

Gale Andrews







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Tested on: 1/19/2007 12:37:31 AM




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