Effect Menu
To apply an effect, select part or all of the tracks you want to modify, and select the effect from the menu. Titles which end in an ellipsis (...) will bring up a dialog asking you for more parameters.
Classes of Effect
There are five classes of effects - the built-in Effects, and four classes of plug-in effects which allow you to download and install additional effects. All classes of effect are applied in the same way. The effects classes are:
- Built-in Effects
- Nyquist Effect Plug-ins
- LADSPA Effect Plug-ins
- VST Effect Plug-ins (Windows and Mac only)
- Audio Unit Plug-ins (Mac only)
List of Built-in Effects
Most of the built-in effects have a "Preview" button. This allows you to listen to how the first three seconds of the selected audio will sound with your effect applied. If it does not sound quite as you want, adjust the controls of the effect and preview again. The preview length can be changed on the Playback tab of Preferences.
Amplify...
This effect increases or decreases the volume of the audio you have selected. When you open the dialog, Audacity automatically calculates the maximum amount you could amplify the selected audio without causing clipping (distortion caused by trying to make the audio too loud).
Auto Duck...
Reduces (ducks) the volume of one or more tracks whenever the volume of a specified "control" track reaches a particular level. Typically used to make a music track softer whenever speech in a commentary track is heard.
BassBoost...
This is a smooth filter which can amplify the lower frequencies while leaving most of the other frequencies alone. It behaves just like the bass control on a stereo. As with Equalization, amplifying particular frequencies can result in clipping, so it is recommended to the track(s) first to -3 dB or lower. If necessary you can always the Bass Boost, Normalize again to a lower level, then re-apply Bass Boost.
Change Pitch...
Change the pitch of a track without changing its tempo.
Change Speed...
Change the speed of a track, also changing its pitch.
Change Tempo...
Change the tempo of a selection without changing its pitch.
Click Removal...
Click Removal is designed to remove individual clicks on audio tracks and is especially suited to declicking recordings made from vinyl records, without damaging the rest of the audio. It will usually work best on very short clicks. For broader individual pops, you could try the Repair effect.
Compressor...
Compresses the dynamic range by two alternative methods. The default "RMS" method makes the louder parts softer, but leaves the quieter audio alone. The alternative "peaks" method makes the entire audio louder, but amplifies the louder parts less than the quieter parts. Make-up gain can be applied to either method, making the result as loud as possible without clipping, but not changing the dynamic range further.
Echo...
Repeats the selected audio again and again, normally softer each time. The delay time between each repeat is fixed, with no pause in between each repeat. For a more configurable echo effect with a variable delay time and pitch-changed echoes, see Delay...
Equalization...
Adjusts the volume levels of particular frequencies.
Fade In
Applies a fade-in to the selected audio, so that the amplitude changes gradually from silence at the start of the selection to the original amplitude at the end of the selection. The shape of the fade is linear. The rapidity of the fade-in depends entirely on the length of the selection it is applied to.
Fade Out
Applies a fade-out to the selected audio, so that the amplitude changes gradually from the original amplitude at the start of the selection down to silence at the end of the selection. The shape of the fade is linear. The rapidity of the fade-out depends entirely on the length of the selection it is applied to.
- By repeating a fade in, the audio will remain quiet for longer then rise more rapidly to the original level. Similarly, repeating a fade out will cause the level to initially drop more rapidly then tail off at a lower level. As with other effects, the fade may be repeated as required by pressing CTRL + R.
For a more customizable exponential fade in or fade out, use the Envelope Tool on Tools Toolbar.
- When cross-fading, fade in the first two-thirds of the overlapping audio that is beginning, and fade out the last two-thirds of the overlapping audio that is coming to an end. Two-thirds is a guideline rather than a rule, but helps to keep the level of audio constant through the fade. Alternatively, cross-fade using the two Cross Fade effects, selecting the entire overlap.
Invert
This effect flips the audio samples upside-down. This normally does not affect the sound of the audio at all. It is occasionally useful for vocal removal.
Leveller...
- Bill 27Aug2012: I would hope that the Leveller will soon be dropped from Audacity. If I understand the history correctly, this was added for use with CleanSpeech at a quick and dirty (very dirty!) compressor that could be used in a chain. It introduces unacceptable distortion (IMO) when used as a compressor. It has some (very limited) use as a "distorted vocal" effect. So, I'd rather lobby for its removal rather than spend more time documenting it.
- Peter 5Nov12: I see no rush to remove "Leveller" from the Audacity repertoire - so I went ahead and documented this effect notwithstanding Bill's comments. And I added the link as Bill had suggested.
- Gale 10Nov12: I agree, while it's there which I think it will probably be for some time, it ought to be documented. BTW with fairly quiet audio with good dynamic range, most settings do not make the loud parts quieter, just increase them a little less, so I changed that text.
Leveller is a simple, combined compressor and limiter effect for reducing the dynamic range of audio. It reduces the difference between loud and soft, making the audio easier to hear in noisy environments or on small loudspeakers. It is best suited to speech recordings but at heavier settings or used multiple times it can also be used as a simple distortion effect for voices or instruments.
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. More details here.
Normalize...
Use the Normalize effect to set the maximum amplitude of a track, equalize the amplitudes of the left and right channels of a stereo track and optionally remove any DC Offset from the track.
Nyquist Prompt...
This brings up a dialog where you can enter Nyquist commands. Nyquist is a programming language for producing and processing audio. For more information see Nyquist Plug-ins Reference.
Paulstretch...
Use Paulstretch only for an extreme time-stretch or "stasis" effect. This may be useful for synthesizer pad sounds, identifying performance glitches or just creating interesting aural textures. Use Change Tempo or Sliding Time Scale rather than Paulstretch for tasks like slowing down a song to a "practice" tempo.
Phaser...
The name "Phaser" comes from "Phase Shifter", because it works by combining phase-shifted signals with the original signal. The movement of the phase-shifted signals is controlled using a Low Frequency Oscillator (LFO).
Repair
Fix one particular short click, pop or other glitch no more than 128 samples long.
Repeat...
Repeats the selection the specified number of times.
Reverse
This effect reverses the selected audio.
Sliding Time Scale / Pitch Shift...
This effect allows you to make a continuous change to the tempo and/or pitch of a selection by choosing initial and/or final change values.
Time Tracks can be used to bend tempo more flexibly (also affecting pitch) using Envelope Tool.
Truncate Silence...
Automatically try to find and eliminate audible silences. Don't use with faded audio.
Wahwah...
Rapid tone quality variations, like that guitar sound so popular in the 1970's.
This effect uses a moving bandpass filter to create its sound. A low frequency oscillator (LFO) is used to control the movement of the filter throughout the frequency spectrum.
The WahWah effect automatically adjusts the phase of the left and right channels when given a stereo recording, so that the effect seems to travel across the speakers.
The following four classes of effect always appear underneath the divider in the Effect menu. Released builds of Audacity include sample Nyquist and/or LADSPA effects.
Nyquist Effects
ToDo Not a priority for 2.0, but needs a little more here:
- where to get docs
- the debug button in Nyquist effects
- Nyquist workbench
- Steve 25Apr12: Does "Nyquist Workbench" fit on this page? When installed it is listed in the menu.
Nyquist plug-ins provide most of the optional effects underneath the divider in the Effect menu. They are also used to provide some of Audacity's built-in audio generators and analysis tools. A wide range of additional Nyquist effect, generation and analysis plug-ins can be obtained from Download Nyquist Plug-ins on our Wiki.
- To add a Nyquist plug-in, put it in the Audacity "Plug-ins" folder.
- On Windows and OS X the "Plug-ins" folder is in the directory where Audacity resides - usually C:\Program Files on Windows or the "Applications" folder on OS X.
- On Linux, the "plug-ins" folder is in usr/share/audacity if you installed an Audacity package supplied by your distribution, or usr/local/share/audacity if you compiled Audacity from source code. Optionally a plug-in folder can be created in the home directory ~/.audacity-files/plug-ins.
- The next time you launch Audacity, plug-ins you added will appear in the Effect, Generate or Analyze menus as appropriate.
The following sample Nyquist plug-ins are included in released builds of Audacity:
Clip Fix...
This effect attempts to reconstruct clipped regions by interpolating the lost signal.
Cross Fade In
This fade applies a curve that will result in equal volume throughout the fade once the faded in and faded out regions are mixed.
Cross Fade Out
This fade applies a curve that will result in equal volume throughout the fade once the faded in and faded out regions are mixed.
Delay...
A configurable delay effect with variable delay time and pitch shifting of the delays.
High Pass Filter...
Passes frequencies above its cut-off frequency and attenuates frequencies below its cut-off frequency; this can be used to reduce low frequency noise.
Low Pass Filter...
Passes frequencies below its cut-off frequency and attenuates frequencies above its cut-off frequency; this can be used to reduce high pitched noise.
Notch Filter...
Greatly attenuate ("notch out") a narrow frequency band. This is a good way to remove mains hum or a whistle confined to a specific frequency with minimal damage to the remainder of the audio.
Tremolo...
Modulates the volume of the selection at the depth and rate selected in the dialog. The same as the tremolo effect familiar to guitar and keyboard players.
Vocal Remover (for center-panned vocals)...
Attempts to remove center-panned audio from a stereo track; vocals are often (but not always) recorded in this way. Vocals (or other audio) can only be removed with this plug-in when panned to center, in other words sounding equally loud in both left and right channels. Help text is available from within the effect's dialog box.
Vocoder...
Vocoder synthesizes a modulator (usually a voice) in the left channel of a stereo track with a carrier wave in the right channel to produce a modified version of the left channel. Vocoding a normal voice with white noise as provided in the effect will produce a robot-like voice for special effects. Other carriers can be used for subtly different voices. Vocoder can only be applied to unsplit stereo tracks.
LADSPA Effects
LADSPA (Linux Audio Developer's Simple Plugin API) plug-ins were originally developed for the Linux platform, but ports of some plug-ins are available for Windows and OS X as well. Most LADSPA plug-ins are effects, but they are also used to provide some of Audacity's built-in audio generators and can be used for audio analysis. Additional LADSPA plug-ins can be downloaded for Windows, OS X and Linux.
- To add a LADSPA plug-in, put it in the Audacity "Plug-ins" folder.
- On Windows and OS X the "Plug-ins" folder is in the directory where Audacity resides - usually C:\Program Files on Windows or the "Applications" folder on OS X.
- On Linux, the "plug-ins" folder is in usr/share/audacity if you installed an Audacity package supplied by your distribution, or usr/local/share/audacity if you compiled Audacity from source code.
- The next time you launch Audacity, plug-ins you added will appear in the Effect, Generate or Analyze menus as appropriate.
Three sample LADSPA effects are included with Windows and Mac builds of Audacity:
Hard Limiter...
An extreme Compressor effect. It can sometimes be used to remove stubborn clicks.
GVerb...
A reverb plug-in that adds ambience or "hall effect". Tips and example settings are available on our Wiki.
SC4...
A stereo compressor with a variable envelope follower for RMS / peak behavior.
- All operating systems: The path specified by the LADSPA_PATH environment variable
- additionally on OS X:
- ~/Library/Audio/Plug-Ins/LADSPA
- /Library/Audio/Plug-Ins/LADSPA
- additionally on Linux/Unix:
- $INSTALL_PREFIX/ladspa
- /usr/local/lib/ladspa
- $LIBDIR/ladspa
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Effects in the following VST and Audio Units (Mac only) classes are always third-party plug-ins added by the user (and also by the operating system in case of Audio Units) |
VST Effects
To add a VST effect on Windows or Mac, put its binary file (for example, the .dll file on Windows) in the Audacity "Plug-ins" folder. The "Plug-ins" folder should be in the same directory where Audacity resides.
- Launch Audacity and go to the Effects tab of Preferences
- Check Rescan VST effects next time Audacity is started and click OK
- Quit and re-launch Audacity - the plug-ins you added will appear in the Effect menu
Note that the Rescan VST effects next time Audacity is started preference will now be un-checked. Audacity caches information about available VST effects rather than slow down each launch by scanning for VST effects. Therefore each time you add a new VST plug-in, it will be necessary to enable a launch-time rescan in Preferences.
When scanning, Audacity also looks for VST plug-ins in the following system locations:
- Windows and OS X: The path specified by the VST_PATH environment variable
- additionally on Windows:
- Windows Registry key HKCU\Software\VST\VSTPluginsPath
- Windows Registry key HKLM\Software\VST\VSTPluginsPath
- additionally on OS X:
- ~/Library/Audio/Plug-Ins/VST
- /Library/Audio/Plug-Ins/VST
Audio Unit Effects
Audio Units (AU) are a system-level plug-in architecture provided on Mac OS X computers. To add an Audio Unit effect, place it in either of the following system plug-in directories:
- ~/Library/Audio/Plug-Ins/Components (user plug-ins)
- /Library/Audio/Plug-Ins/Components (system-wide plug-ins)
The next time you launch Audacity, newly added plug-ins will appear underneath the divider in the Effect menu.
