Effect Menu/it

Audacity includes many built-in effects and also lets you use a wide range of plug-in effects. You can download many free plug-ins for Audacity from http://web.audacityteam.org/download/plugins and the links thereon. 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
Audacity's built-in effects (those that appear in the program irrespective of the contents of your Audacity and other Plug-ins folders) are above the divider in the Effect menu. 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.

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.

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 linear fade-in to the selected audio - the rapidity of the fade-in depends entirely on the length of the selection it is applied to. For a more customizable logarithmic fade, use the Envelope Tool on the Tools Toolbar.

Fade Out
Applies a linear fade-out to the selected audio - the rapidity of the fade-out depends entirely on the length of the selection it is applied to. For a more customizable logarithmic fade, use the Envelope Tool on the Tools Toolbar.

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 example when the left and right channels of a song both contain equal amounts of vocals, but unequal amounts of background instruments. By inverting one of the channels and not the other and then converting from stereo to mono, the vocals will cancel each other out, leaving just the instrumentals. This only works if the exact same vocal signal is present in both of the channels to begin with.

Leveler...
The Leveler effect makes quiet passages louder and loud passages quieter. It does this in a way that is different from the Compressor effect. As a result it does add some distortion to the processed audio. The only way to be sure if the effect does what you want is to try it. For example, applying this effect twice at its Heaviest setting on a normally-recorded voice can produce an "air traffic controller" effect.

Noise Reduction...
This effect is ideal for reducing 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 Audacity and Nyquist and Nyquist in Audacity.

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 very 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 temporally; after the effect the end of the audio will be heard first and the beginning last. Some people reverse small portions of audio to make inappropriate language unintelligible, while others believe you can hear subliminal messages if you listen to speech backwards. You can also create interesting sound effects by recording natural events and reversing the 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 intial and/or final change values.

Tempo changes made without selecting a pitch change preserve the original pitch, and pitch changes made without selecting a tempo change preserve the original tempo. By changing only one of tempo and pitch and choosing the same initial and final value, you can use Sliding Time Scale / Pitch Shift in the same way as Change Tempo or Change Pitch to produce a high quality fixed change. However Sliding Time Scale / Pitch Shift lets you for example set the initial tempo change to -50% while also setting the final tempo change to +20%, the initial pitch change to +3 semitones and the final pitch change to +1 semitones.

Because of the high quality algorithm used, Sliding Time Scale / Pitch Shift is normally slower compared to performing the same effect with Change Tempo or Change Pitch.

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
Nyquist plug-ins provide most of the optional effects underneath the divider in the Effect menu. They are 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.
 * 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 ...
Clip Fix attempts to reconstruct clipped regions by interpolating the lost signal.

Cross Fade In
Despite the name this effect does not do an automatic crossfade between two tracks or clips. Instead it applies a curve that is different from the one used by the Fade In effect. The curve used is one that will result in equal volume throughout the fade once the faded in and faded out regions are mixed.

Cross Fade Out
Despite the name this effect does not do an automatic crossfade between two tracks or clips. Instead it applies a curve that is different from the one used by the Fade Out effect. The curve used is one 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 cutoff frequency and attenuates frequencies below its cutoff frequency.

Low Pass Filter...
Passes frequencies below its cutoff frequency and attenuates frequencies above its cutoff frequency.

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...
Synthesizes audio (usually a voice) in the left channel of a stereo track with a carrier wave (typically white noise) in the right channel to produce a modified version of the left channel. Vocoding a normal voice with white noise will produce a robot-like voice for special effects. Other carriers can be used for subtly different robot voices, such as a sawtooth tone or a synthesized string chord.

Vocoder only works on unsplit stereo tracks. Example steps to make a stereo voice sound like a robot:
 * 1) Record or import your stereo voice track
 * 2) Click the Audio Track Dropdown Menu > Split Stereo Track to split the stereo track into left and right channels
 * 3) Click the Track Control Panel of the right channel to select it, then click Generate > Noise... and choose  White Noise
 * 4) On the left (upper) channel, click the Track Dropdown Menu > Make Stereo Track to make an unsplit track again
 * 5) Click the Track Control Panel once more to select the track, then Effect > Vocoder... . Try with the default settings at first. If you want to make the voice sound less intelligible, reduce the number of vocoder bands and vice versa.

If your voice track is mono:
 * 1) Click Tracks > Add New > Mono Track to add a new track underneath your voice track
 * 2) Click Generate > Noise... and choose White Noise
 * 3) Then follow steps 4 and 5 above

LADSPA Effects
LADSPA (Linux Audio Developer's Simple Plug-in 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.

GVerb...
A reverb plug-in. Tips and example settings are available on our Wiki.

SC4...
A stereo compressor with a variable envelope follower for RMS / peak behavior.

Audacity will also load LADSPA plug-ins from the following system locations:
 * 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

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.
 * 1) Launch Audacity and go to the Effects tab of Preferences
 * 2) Check Rescan VST effects next time Audacity is started and click OK
 * 3) 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.