Effect Menu

Does our compressor make "soft sounds louder"? Only if you normalize? - Gale

Audacity includes many built-in effects and also lets you use a wide range of plug-in effects. You can download many free plugins for Audacity on http://audacity.sourceforge.net/download/plugins. More information is also available at http://www.kvr-vst.com, http://www.plugin.org.uk/ and http://www.ladspa.org/. 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.

ToDo Move and merge anything useful in the old Noise Removal text (greyed out in the detailed text) into Noise Removal.

Classes of Effect

There are four classes of effects - the built-in Effects, and three classes of plug-in effect which allow you to download and install additional effects. All classes of effect are applied in the same way. The four effects classes are:

Mac users also have access to Audio Unit effects. Do we want to note that here, or further down under LADSPA effects?

• Built-in Effects
• VST Effect Plug-ins
• Nyquist Effect Plug-ins
• LADSPA Effect Plug-ins

Purpose of Effects

Effects in any of the four classes can perform similar tasks. These are Audacity's built-in effects grouped by purpose:

Volume changes

(no effect on tone quality)

Amplify    Auto Duck    Compressor    Fade In    Fade Out    Leveller    Normalize    Cross Fade In    Cross Fade Out

Tone changes

Bass Boost    Echo    Equalization    Phaser    Wahwah    Delay    High Pass Filter    Low Pass Filter    Tremolo    Vocoder

Pitch and tempo changes

Change Pitch without changing tempo; Change Tempo without changing pitch; Change Speed affecting pitch and tempo

Audio restoration

Click Removal    Noise Removal    Repair    Truncate Silence    Clip Fix   

Other built-in effects

Invert    Nyquist Prompt    Repeat    Reverse

Most built-in effects have a "Preview" button. This allows you to listen to how the first three seconds of your selected audio will sound with your effect applied. If it does not sound quite as you want, simply adjust the controls of the effect and preview again. The preview length can be changed on the Playback tab of Preferences.

Generate and Analyze plug-ins

Nyquist plug-ins are also used to provide some of Audacity's built-in audio generators and analysis tools. You can similarly add either Nyquist or LADSPA generation and analysis plug-ins to Audacity which will then appear under the Generate or Analyze Menu.

List of Built-in Effects

ToDo I am surprised that Audacity does not ship with a reverb effect, not even GVerb - Bill

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...

ToDo - is this description appropriate?

Compresses the dynamic range by making the loud parts softer. If make-up gain is applied the effect will also make the quiet parts louder.

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.

Do we want this image here? It is NOT showing the use of the envelope tool as implied by the preceding text. I don't think we need images for these simple fade effects, and I don't think they need their own pages. - Bill

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.

Leveller...

ToDo - is this description appropriate?

The Leveller 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 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...

ToDo - is this description appropriate?

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).

ToDo - needs its own page

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

ToDo

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.

VST Effects

• To use a VST plug-in effect, put the effect in the directory (folder) called "Plug-Ins", which should be in the same directory where Audacity resides. If there is no directory, create one.

These instructions no longer apply, right?

• You will also need to download and unzip the [Enabler] To do: broken link to the same directory.
• The next time you launch Audacity, any plug-ins you added will appear in the Effect menu.

• Launch Audacity and go to the Effects tab of the Preferences dialog. Check Rescan VST effects next time Audacity is started. Click the OK button.
• Quit and re-launch Audacity - any plug-ins you added will appear in the Effect menu.
• The Rescan VST effects next time Audacity is started option will now be un-checked.

Since scanning for VST effects slows the launch process, Audacity can launch faster if it doesn't have to do this scan unless the user explicitly asks for it.

Nyquist Effects

• To use a Nyquist effect, put the effect in the directory (folder) called "Plug-Ins", which should be in the same directory where Audacity resides. Upon installation, some nyquist scripts are included, so you needn't worry about creating this directory.
• The next time you launch Audacity, any plug-ins you added will appear in the Effect, Generate or Analyze menus.

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 cross fade 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.

The details of how to use this in conjunction with the Cross Fade Out effect to make equal-volume cross fades is left as an exercise for the reader ? - Bill

Cross Fade Out

Despite the name this effect does not do an automatic cross fade 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.

The details of how to use this in conjunction with the Cross Fade In effect to make equal-volume cross fades is left as an exercise for the reader ? - Bill

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.

ToDo Does this need its own page? - Bill

Low Pass Filter...

Passes frequencies below its cutoff frequency and attenuates frequencies above its cutoff frequency.

ToDo Does this need its own page? - Bill

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.

ToDo Does this really need its own page? - Bill

Vocal Remover

Attempts to remove center-panned vocals from a stereo track. Help text is available from within the dialog.

Vocoder

Turn a normal voice into a robotic voice.

ToDo I believe that this is a phase vocoder http://en.wikipedia.org/wiki/Phase_vocoder. I've played with it a bit but really have no idea how to describe it. - Bill

LADSPA Effects

These originally started out in a Linux plugin format under the Linux Audio Developer's Simple Plugin API, but can now be used in Windows and OS X as well. There are lots of free plugins available, and no enabler is needed. More information can be found ladspa.org and the Audacity Plug-ins and Libraries page.

ToDo additional plug-ins included in Windows and Mac release builds

Getting a good reverb sound depends a lot on the source audio and can take a lot of experimentation. One good strategy is to select a small portion of audio (a few seconds) and try to add reverb. Listen to it, then Undo and try it again with different settings. Keep doing this until you've found the settings you like the sound of best, and then Undo one last time, Select All, then apply the effect to your entire recording.