(sonicArts) Audacity tips

Because I haven’t written a full post on how to use Audacity, I thought I would at least put up some tips for common tasks.

Signal Processing

In Peak, most of your processing commands are in the DSP menu, with plugins in a separate Plugins menu. In Audacity, most of your processing commands are in the Effects menu, including plugins. All processing in Audacity is destructive (even from plugins). Once you click OK in the process dialog window, the effect is applied to your file.

Gain Envelopes

Applying a changing gain function over time is done within the audio file in audacity, using “rubber-band” style editing. First, change to the Envelope Tool for editing.

The track display changes slightly, showing slightly blue-ish amplitude envelope bands running throughout the length of the audio display. Click on the band to add a breakpoint for editing. Drag the breakpoint to make an envelope change.

These gain changes are non-destructive – that is, they do not change what is stored in the audio file. The change in gain is applied in real time during playback. If you want to have the gain envelope change applied permanently (destructively), you must choose the Mix and Render command from the Tracks menu.

Cropping Audio

To delete all but the selected audio (cropping), use the Edit | Remove Audio | Trim command.

Changing Speed and Pitch

Audacity uses the Change Speed command to change playback speed so that pitch is also affected. What is confusing (when compared to most other audio editors/processors), is that you specify the playback ratio as a percentage of change. Most audio editors/processors consider 100% playback speed to be unity playback (played back at original speed). 200% playback speed would be twice the playback rate as unity, shifting the pitch up an octave and only taking half as long to play through the file. 50% playback speed would be half the original speed, shifting the pitch down an octave and taking twice as long to play the file.

Audacity uses the percentage of change to be applied to the playback rate.  Applying a 100% speed change will cause playback to be at twice the original rate, and shift the pitch up one octave. Applying a -50% change will cause the speed to playback at half the rate, and drop the pitch down an octave. The easiest way to convert percentage change to playback percentage is to add the change to 100%.

A 200% change of speed adds to the original 100% playback ratio to result in a 300% playback ratio. 100% + 200% = 300%

A -75% change of speed results in a 25% playback ratio. 100% + (-75%) = 25%


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