20
have a Preview button. Clicking on this button plays up to three seconds of audio, allowing you to
hear what it will sound like after the effect is applied. This is useful for fine-tuning the effect
parameters.
Repeat Last Effect - selecting this command is a shortcut to applying the most recent effect with the
same settings. This is a convenient way to quickly apply the same effect to many different parts of a
file.
Amplify - changes the volume of the selected audio. If you click the "Allow clipping" checkbox, it will
let you amplify so much that the audio ends up beyond the range of the waveform, and is clipped
(distorted). The default value when you open the effect is to amplify so that the loudest part of the
selection is as loud as possible without distortion.
Bass Boost - enhances the bass frequencies in the audio.
Change Pitch - changes the pitch/frequency of the selected audio without changing the tempo.
When you open the dialog, the starting frequency is set to Audacity's best guess as to the frequency
of the selection. This works well for recordings of singing or musical instruments without background
noise. You can specify the pitch change in one of four different ways: musical note, semitones,
frequency, or percent change.
Change Speed - changes the speed of the audio by resampling. Making the speed higher will also
increase the pitch, and vice versa. This will change the length of the selection.
Change Tempo - changes the tempo (speed) of the audio without changing the pitch. This will
change the length of the selection.
Compressor - compresses the dynamic range of the selection so that the loud parts are softer while
keeping the volume of the soft parts the same. You can optionally normalize the recording
afterwards, resulting in the entire piece having higher perceived volume.
Echo - very simple effect that repeats the selection with a decay, sounding like a series of echoes.
This effect does not change the length of the selection, so you may want to add silence to the end of
the track before applying it (using the Generate Menu).
Equalization - Boost or reduce arbitrary frequencies. You can select one of a number of different
curves designed to equalize the sound of some popular record manufacturers, or draw your own
curve.
Fade In - fades the selection in linearly
Fade Out - fades the selection out linearly
FFT Filter - similar to Equalization, lets you enhance or reduce arbitrary frequencies. The curve here
uses a linear scale for frequency.
Invert - Flips the waveform vertically, the same as a phase inversion in the analogue domain.
Noise Removal - This effect lets you clean up noise from a recording. First, select a small piece of
audio that is silent except for the noise, select "Noise Removal", and click on the "Get Noise Profile"
button. Then select all of the audio you want filtered select "Noise Removal" again, and click the
