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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 normalise 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 echos. 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 "Remove Noise" button. You can experiment with the slider to try to
remove more or less noise. It is normal for Noise Removal to result in
some distortion. It works best when the audio signal is much louder than
the noise.
Normalize - allows you to correct for DC offset (a vertical displacement of
the track) and/or amplify such that the maximum amplitude is a fixed
amount, -3 dB. It's useful to normalize all of your tracks before mixing. If
you have a lot of tracks, you may then need to use the track gain sliders to
turn some down.
Nyquist Prompt - for advanced users only. Allows you to express arbitrary
transormations using a powerful functional programming language. See
the Nyquist section of the Audacity website for more information.
