Index of Effects, Generators and Analyzers - Audacity Development Manual

# Index of Effects, Generators and Analyzers

From Audacity Development Manual

This page is a quick index to the Effects, Generators and Analyzers shipped with Audacity. You may also add new plug-ins in various popular formats.

- An Effect changes the audio in some way.
- A Generator creates new audio, either in an existing track or in a new track.
- An Analyze tool performs analysis on a selection of audio - it does not change the audio and does not create new audio.

Although by default, no keyboard shortcuts are provided for most Effect, Generate or Analyze commands, it is possible to set up your own shortcut for any of these commands. For instructions on how to do this please see Keyboard Preferences.

See this page for tips on Navigating Effects without using a mouse.

| When playing, recording or paused, the Effect menu will appear grayed out, because changes to the audio data cannot be made until you press the Stop button .

## Alphabetical Index of Effects, Generators and Analyzers

Adjustable Fade Contrast Limiter Repeat Spectral edit parametric EQ
Amplify Crossfade Clips Low Pass Filter Reverb Spectral edit shelves
Auto Duck Crossfade Tracks Noise Reverse Studio Fade Out
Bass and Treble Delay Noise Reduction Rhythm Track Tone
Beat Finder Distortion Normalize Risset Drum Tremolo
Change Pitch DTMF Tones Notch Filter Sample Data Export Truncate Silence
Change Speed Echo Nyquist Prompt Sample Data Import Vocal Reduction and Isolation
Change Tempo Equalization Paulstretch SC4 Vocal Remover (legacy)
Chirp Fade In Phaser Silence Vocoder
Classic Filters Fade Out Plot Spectrum Silence Finder Wahwah
Click Removal Find Clipping Pluck Sliding Time Scale / Pitch Shift
Clip Fix High Pass Filter Regular Interval Labels Sound Finder
Compressor Invert Repair Spectral edit multi tool

Where an effect, generator or analyzer has settings, its description page (accessed by the links below) shows an image of the interface and its default settings.

## Add / Remove Plug-ins...

Selecting this option from the Effect Menu (or the Generate Menu or Analyze Menu) takes you to a dialog where you can enable or disable particular Effects, Generators and Analyzers in Audacity. Even if you do not add any third-party plug-ins, you can use this to make the Effect menu shorter or longer as required. For details see Add / Remove Effects, Generators and Analyzers.

By default all the built-in effects, with the exception of Classic Filters, are enabled in Audacity.

Additional plug-ins can also be loaded into Audacity:

- Installing Nyquist plug-ins on Windows, Mac or Linux
  - See also this list of downloadable Nyquist plug-ins
- Installing VST plug-ins on Windows, Mac or Linux
- Other types of plug-in.

## Effects by Function

See the Effect Menu for further details.

### Make the sound louder or quieter

- Amplify: Increases or decreases the volume of the audio you have selected.
- 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.
- 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.
- Limiter: Limiter passes signals below a specified input level unaffected or gently reduced, while preventing the peaks of stronger signals from exceeding this threshold. Mastering engineers often use this type of dynamic range compression combined with make-up gain to increase the perceived loudness of an audio recording during the audio mastering process.
- 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.
- SC4: This effect is a stereo compressor with a variable envelope follower for RMS (average) / peak behavior.

Although shipped as part of Audacity, SC4 is not enabled by default. To enable it for use you will need to use Add/Remove Plugins... from the top of the Effect menu. See this page for details.

### Fade a section in or fade it out

- Crossfade Clips: Use Crossfade Clips to apply a simple crossfade to a selected pair of clips in a single audio track.
- Crossfade Tracks: Use Crossfade Tracks to make a smooth transition between two overlapping tracks one above the other. Place the track to be faded out above the track to be faded in then select the overlapping region in both tracks and apply the effect.
- 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.
- Studio Fade Out: Applies a more musical fade out to the selected audio, giving a more pleasing sounding result.
- Adjustable Fade: enables you to control the shape of the fade (non-linear fading) to be applied by adjusting various parameters; allows partial (that is not from or to zero) fades up or down.

For a discussion of what the different types of fade do, see Fades.

### Change the quality of the sound

- Bass and Treble: Increases or decreases the lower frequencies and higher frequencies of your audio independently; behaves just like the bass and treble controls on a stereo system.
- Classic Filters: Offers three different types of filter which together emulate the vast majority of analog filters, providing a useful graphical tool for analysis and measurement. This effect is not enabled by default. To enable it, use Effect > Add / Remove Plug-ins... to open the Plug-in Manager: Effects, Generators and Analyzers dialog.
- Distortion: Use the Distortion effect to make the audio sound distorted. By distorting the waveform the frequency content is changed, which will often make the sound "crunchy" or "abrasive". Technically this effect is a waveshaper. The result of waveshaping is equivalent to applying non-linear amplification to the audio waveform. Preset shaping functions are provided, each of which produces a different type of distortion.
- Equalization: Adjusts the volume levels of particular frequencies.
- 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.
- 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).
- Spectral edit parametric EQ: When the selected track is in spectrogram or spectrogram log(f) view and the spectral selection has a center frequency and an upper and lower boundary, performs the specified band cut or band boost. This can be used as an alternative to Equalization or may also be useful to repair damaged audio by reducing frequency spikes or boosting other frequencies to mask spikes.
- Spectral edit shelves: When the selected track is in spectrogram or spectrogram log(f) view, applies either a low- or high-frequency shelving filter or both filters, according to the spectral selection made. This can be used as an alternative to Equalization or may also be useful to repair damaged audio by reducing frequency spikes or boosting other frequencies to mask spikes.
- 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.
- 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.
- Wahwah: Rapid tone quality variations, like that guitar sound so popular in the 1970's.

### Repair damaged audio

- Click Removal: Click Removal is designed to remove clicks on audio tracks and is especially suited to declicking recordings made from vinyl records.
- Clip Fix: Clip Fix attempts to reconstruct clipped regions by interpolating the lost signal.
- 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.
- 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.
- Repair: Fix one particular short click, pop or other glitch no more than 128 samples long.
- Spectral edit multi tool: When the selected track is in spectrogram or spectrogram log(f) view, applies a notch filter, high pass filter or low pass filter according to the spectral selection made. This effect can also be used to change the audio quality as an alternative to using Equalization.

### Make the sound faster, slower, lower pitched or higher pitched

- Change Pitch: Change the pitch of a selection without changing its tempo.
- Change Speed: Change the speed of a selection, also changing its pitch.
- Change Tempo: Change the tempo and length (duration) of a selection without changing its pitch.
- 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.
- 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.
- Truncate Silence: Automatically try to find and eliminate audible silences. Don't use with faded audio.

### Add reverberation or echo

- Delay: A configurable delay effect with variable delay time and pitch shifting of the delays.
- Echo: Repeats the selected audio again and again, normally softer each time and normally not blended into the original sound until some time after it starts. 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.
- Reverb: A configurable stereo reverberation effect with built-in and user-added presets. It can be used to add ambience (an impression of the space in which a sound occurs) to a mono sound. Also use it to increase reverberation in stereo audio that sounds too "dry" or "close".

For details of the underlying principles of delay and reverb effects please see this page in the Wiki.

### Remove vocals

- 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.
- Vocal Reduction and Isolation: Attempts to remove or isolate center-panned audio from a stereo track. Most "Remove" options in this effect preserve the stereo image.
- Vocal Remover: (Legacy effect) Attempts to remove center-panned vocals from a stereo track. The output from this effect will always be mono. Help text is available from within the dialog.

### Manipulate Audio

- Repeat: Repeats the selection the specified number of times.
- Reverse: Reverses the selected audio; after the effect the end of the audio will be heard first and the beginning last.

### Invoke Nyquist

- Nyquist Prompt: Brings up a dialog where you can enter Nyquist commands. Nyquist is a programming language for generating, processing and analyzing audio. For more information see Nyquist Plug-ins Reference.

## Generators by Function

See the Generate Menu for further details.

### Generate Tones

- Chirp: Generates four different types of tone waveform like the Tone Generator, but additionally allows setting of the starting and ending amplitude and frequency.
- DTMF Tones: Generates dual-tone multi-frequency (DTMF) tones like those produced by the keypad on telephones.
- Tone: Generates one of four different tone waveforms: Sine, Square, Sawtooth or Square (no alias), and a frequency between 1 Hz and half the current project rate.

### Generate Silence or Noise

- Noise: Generates 'white', 'pink' or 'brown' noise.
- Silence: Creates audio of zero amplitude, the only configurable setting being duration.

### Generate Instruments or Metronome

- Rhythm Track: Generates a track with regularly spaced sounds at a specified tempo and number of beats per measure (bar).
- Pluck: A synthesized pluck tone with abrupt or gradual fade-out, and selectable pitch corresponding to a MIDI note.
- Risset Drum: Produces a realistic drum sound.

### Generate from Imported Data

- Sample Data Import: Create audio from imported numeric data.

## Analyzers by Function

See the Analyze Menu for further details.

### Analyze Amplitude or Other Audio Properties

- Contrast: Analyzes a single mono or stereo speech track to determine the average RMS difference in volume (contrast) between foreground speech and background music, audience noise or similar. The purpose is to determine if the speech will be intelligible to the hard of hearing.
- Find Clipping: Displays runs of clipped samples in a Label Track, as a screen-reader accessible alternative to View > Show Clipping. A run must include at least one clipped sample, but may include unclipped samples too.
- Plot Spectrum: Takes the selected audio (which is a set of sound pressure values at points in time) and converts it to a graph of frequencies against amplitudes.
- Sample Data Export: Reads the values of successive samples from the selected audio and prints this data to a plain text, CSV or HTML file. Further information may be added as a "header" at the top of the file.

### Divide Up Sounds or Silences using Labels

- Regular Interval Labels: Places labels in a long track so as to divide it into smaller, equally sized segments.
- Silence Finder: Divides up a track by placing point labels inside areas of silence.
- Sound Finder: Divides up a track by placing region labels for areas of sound that are separated by silence.

### Mark Beats using Labels

- Beat Finder: Attempts to place labels at beats which are much louder than the surrounding audio. It's a fairly rough and ready tool, and will not necessarily work well on a typical modern pop music track with compressed dynamic range. If you do not get enough beats detected, try reducing the "Threshold Percentage" setting.