Audacity Effects: Amplify (1) – Basic Operations


The Amplify effect is similar to Normalize effect. Amplify allows you to amplify a track or tracks by a certain level whereas Normalize sets the peak amplitude to a certain level. Optionally, Amplify can also set peak amplitude to a chosen level, in which case it is really the same as Normalize, for single track that is. For multiple tracks, Amplify and Normalize behave differently.

To understand the effect of Amplify, as well as to see its difference from Normalize, let us first take a look at Normalize. Below is a small clip from a music track. You can see that the peak is at around -9db.


original signal showing peak amplitude at -9 db

I then applied the Normalize effect to set the peak amplitude to -3 db….


and the figure below shows the waveform after the normalization.1 As you can see, the peak amplitude is indeed set from the original -9 db to the final -3 db. This is how the Normalize effect works.


signal after normalizing to -3 db


If you apply the Amplify effect with -3 db, however, the amplitude of the signal will not be set to -3 db but will be reduced by 3 db, as the following waveform shows. The first figure is before the effect is applied; and the last is after (note the peak is reduced to -12 db).

original signal

original signal showing peak amplitude at -9 db



signal after amplifying by -3 db (note the peak amplitude)

As mentioned, you can also use Amplify to set the maximum amplitude. For that you would use the second parameter in the dialog box. As you change the number, you can also tell that the second number is actually tied to the first. For single track, this has the same effect as normalizing to the same maximum amplitude. This can be clearly seen from the example below.


signal after amplifying, setting peak amplitude to -3 db

signal after amplifying, setting peak amplitude to -3 db

In next article, we will talk about the third parameter, “allow clipping.”

  1. The waveforms are all shown in db scale as this scale shows the effect well.

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