Effect Menu

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 our Website. 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.

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Classes of Effect

There are four classes of effects, the built in Internal effects, and three classes of plug-in effects. They are all applied in the same way. The four effects classes are

• Internal Effects
• VST Effect Plugins
• Nyquist Effects
• LADSPA Effects

Internal Effects

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...

Bass Boost...

This is a safe, smooth filter which can amplify the lower frequencies while leaving most of the other frequencies alone. It is most effective if you don't try to boost too much; 12 dB is usually just right.

Change Pitch...

Change Speed...

Change Tempo...

Click Removal...

Compressor...

Echo...

This effect repeats the audio you have selected again and again, softer each time. There is a fixed time delay between each repeat. You may want to add silence to the end of your track(s) first so that the echo has time to die out. If you't, the echo will stop being heard when the track ends, so you will probably not hear it. When you select "Echo..." from the Effect menu, Audacity will ask you for two numbers.

• The first number is the amount of delay between the echos, in seconds.
• The second value is the decay factor, which is a number between 0 and 1. A decay factor of 0 means no echo, and a decay factor of 1 means that each echo is just as loud as the original. A value of 0.5 means that its amplitude is cut in half each time, so it dies out slowly. Smaller values will make it die out even more quickly.

The Echo effect is very simple and is not intended to be used in place of a Reverb effect, which simulates the sound of a room, concert hall, stage, or other natural environment. Audacity for MacOS and Windows comes with Gverb, a free LASPA Reverb plug-in.

• If you set the decay value to 1.0, you can use Echo to create loops that repeat as long as you want any never change volume.

Equalization...

Fade In

Applies a linear fade-in to the selected audio. For a logarithmic fade, use the envelope tool.

Fade Out

Applies a linear fade-out to the selected audio. For a logarithmic fade, use the envelope tool.

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...

Noise Removal...

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The Noise Removal function in Audacity 1.3.x and higher is greatly improved over the Noise Removal included with Audacity 1.2.x. But with improvement comes a small amount of added complexity for the end user.

In order to use Noise Removal, you need an audio clip with two things:

1. Audio you want to clean up.
2. A section in that audio clip of "silence" that only contains noise.

Using Noise Removal

The procedure for using Noise Removal is as follows:

1. Highlight a section of "silence" and click Effects -> Noise Removal. In this dialog box, click "Get Noise Profile." This will teach Audacity what sort of noise it should be looking for when it attempts to remove it.
2. Now, highlight the selection that you want to remove the noise from and click Effects -> Noise Removal.
3. At this point, we need to find the settings that will work for your signal. Most users can leave the "Frequency Smoothing" and "Attack/decay Time" settings at their default value. It is easiest to set "Noise Reduction" by trial and error, adjusting the slider and using the Preview button to listen to a few seconds of the audio after having that level of noise removed.
4. Once all the settings are in place, click OK and Noise Removal will run.

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 teach the software about the noise, using a portion of your sound which contains all noise and no signal,

where the recording is silent except for the noise.

• In the second you use that information to remove the noise from the rest of the recording.

First off, you need to find a section fo recording that contains only noise, and not any of your wanted sound, or people talking and the like. This doesn't need to be very long, a second is enough, and in necessary you can make it up from several places in the project (using copy and paste). Now 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. Next, select all of the audio where you want the noise removed from and choose Noise Removal... again. In th elower half of the dialog adjust the slider to control how agressive the noise removal is. Most of the time you want a low setting unless the noise is really bad. Finaly, click the "Remove Noise" button to start processing. This may take a little while because it's quite a complex effect to apply.

If too much or not enough noise was removed, you can Undo (from the Edit menu) and try Noise Removal... again with a different noise removal level. You don't have to get a new noise profile again if you think the first one was fine.

Removing noise usually results in some distortion. This is normal and there's virtually nothing you can do about it. When there's only a little bit of noise, and the signal (i.e. the voice or the music or whatever) is much louder than the noise, this effect works well and there's very little audible distortion. But when the noise is very loud, when the noise is variable, or when the signal is not much louder than the noise, then the result is often too distorted.

If you are still having problems then the following tips may help:

• Do any click removal, compression or other effects after doing noise removal, not first. It works best as close to the source of the noise as possible.
• Make the selection you use to teach audacity about the noise a little quieter before you do "Get Profile", using the amplify effect.
• Duplicate your source track before you apply noise removal, and adjust the relative volume of the two tracks to get the best sound quality.

Normalize...

Nyquist Prompt...

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

Repeat...

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.

Truncate Silence...

Wahwah...

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

Freeverb2...

Audacity for Mac OS and Windows comes with a VST plug-in called Freeverb, which is in version 2 (hence "Freeverb2"). This effect implements a versatile and high-quality reverb effect.

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.

There are a lot of parameters to Freeverb2: Room size, Damping, Predelay, Lowpass, Highpass, Wet level, and Dry level.

• Let's start with the wet and dry levels.
  • Freeverb works by taking your audio signal and modifying it to create the reverberated sound, i.e. the sound you hear echoing off the walls of the room. This is called the "wet" part of the effect.
  • This is mixed together with the original sound, which is called the "dry" part of the effect, to produce the combination of direct (unreverberated) and indirect (reverberated) sound, which is what you would naturally hear. If you set the dry level to -infinity and the wet level to 0 dB, the result is something like standing outside of a concert hall: you can only hear the reverberated sound.
  • If you set the dry level to 0 and the wet level to -infinity, it's like standing right in front of the singer in a tiny room - all you can hear is the singer, and no reverb. A good place to start is to set both the dry level and wet level to 0 dB. However, you may want to experiment with lowering the dry level while you are experimenting with the sound of the reverb.
• The room size parameter is self-explanatory. The smallest room size setting creates a quick, bright reverb, while the largest setting creates a long, drawn-out, and dark reverb. The damping parameter controls how the sound bounces off the walls - i.e. if it is mostly reflected or

absorbed.

• The predelay controls the delay between the dry signal (unreverberated) and the wet signal (reverberated) - usually there is some predelay because of the time it takes sound waves to travel from the sound source to the nearest wall, and to the microphone. Larger predelays are suitable for creating an effect of a larger room.
• Finally, the lowpass and highpass filters can be used to make the reverberated sound lower or higher. Increasing the lowpass filter filters out the high frequencies, and similarly increasing the highpass filter filters out the low frequencies.

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.

These are default in all builds of Audacity:

These are included in Windows builds:

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 on the web.

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grouped by category.

Generators

• Chirp: Generates a chirping sound
• DTMF Tones: Creates telephone signaling sounds, or "touch tones"
• Noise: Generates three types of noise
• Silence: Fills a track with however much silence you want
• Tone: Generates a pure tone with whatever frequency you want

Volume levels

These effects don't change the sound quality but just adjust the volume level in different ways

• Amplify: change the volume of the selection
• AutoDuck: if you have two tracks, this lets you turn down one (e.g. the background music) when the other one is loud (e.g. when someone's talking over it)
• Compressor: Compresses the dynamic range by making the soft parts louder, and the loud parts softer
• Fade In
• Fade Out
• Leveller: A different form of dynamic range compression than Compressor
• Normalize: Same as Amplify, but also fixes recordings that have an offset up or down in the waveform, called a DC offset

Tone-changing effects

• Bass Boost - increase bass frequencies
• Echo
• Equalization - adjust the levels at every frequency to boost highs, lows, or anything else
• Phaser
• Wahwah

Pitch and tempo

• Change Pitch - without changing the tempo
• Change Tempo - without changing the pitch
• Change Speed - affecting both pitch and tempo together

Clean-up bad recordings

• Click Removal - automatically find and remove click sounds
• Noise Removal - try to filter out constant background noise
• Repair - fix one particular very short click, pop, or other glitch
• Truncate Silence - automatically try to find and eliminate long periods of silence

Other

• Invert - flip the sound upside down
• Repeat - repeat the selection
• Reverse - turn the sound backwards