In Audacity, we normalize to a level, but amplify by a level. However, in the “amplify” effect, there is also an option for you to amplify to a chosen peak amplitude. When this option is used, “amplify” basically functions the same as “normalize,” but only for single track audio.
Amplification by multiple tracks has been covered before when “normalize” is discussed. Here we are just going to show an example illustrating the difference.
Below is an Audacity project with 2 mono tracks: the top track is my voice reciting some instruction, and the bottom track is the background music. You can see that the background music is set to be much lower in magnitude compared to the voice in order not to overpower the voice.
If I selected both tracks and applied the “normalize” effect (to -2 db in the example), we see that the peak amplitude of both tracks would be set to -2 db (which is about 0.8 in linear scale). That would have make the background music too loud.
If, however we selected both tracks and did the “amplify” effect (also to -2 db), Audacity would find the peak amplitude of both tracks combined and set it to -2 db as can be seen in the figure below. The second track was also affected/amplified, but the balance between the two tracks were maintained, so the background music (bottom track) stayed softer than my voice (top track).
So there it was… just a simple example to show the difference between “amplify” and “normalize” for multi tracks.