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Monday, September 21, 2009

Multitrack audio and creating MP3 podcast files: Podcasting for E-Learning

Today's post about Podcasting for E-Learning covers editing and rendering multitrack audio using the open-source audio editor Audacity.

Click on the play button on the YouTube video to view the demo at 240x320 size (which will give you an overview of the editing techniques I'm using), or click here to view the demo (1024x768, broadband connection recommended) to see the editing techniques in detail. The demo is about seven minutes in duration, and requires Flash Player version 7 or better.

Typically, a podcast has a number of discrete audio tracks:

  • Musical signature tune track
  • Narration voice-over (v/o)
  • Incidental music and / or wildtrack (ambient sounds such as keyboard taps, phones ringing etc)

To create, edit and render a multitrack audio file (called a 'package'):

  1. Open and save a new Audacity project
  2. Name it something like 'My_Podcast_Final'
  3. Using the File menu, open the first track to be played in the sequence (usually the sig tune)
  4. Using the Project >> Import Audio menu add the rest of your clips. Each clip will open on a new track in the Audacity UI
  5. Using the Timeline Shift Tool to move the new tracks to their approximate location on the timeline; you'll refine their location later
  6. Use the Envelope Tool to set the volume at appropriate levels for cross-fades, fade-ins, fade-outs, and for setting music as a soundbed under the voice-over narrative
  7. When you have all the elements of the package aligned to more-or-less where you want them, use the Timeline Shift Tool to refine the timing of the various elements - try to make the clips as "tight" as possible: omit any long silences or caesurae unless they're for dramatic effect.
    If your audience hear a long silence they may well think that they have reached the end of the package and turn off.
  8. Once your package is edited satisfactorily, save it.
  9. Next go to File >> Export as MP3
  10. Enter appropriate metadata in the dialog box and click on Save.
  11. An MP3-formatted version of your project file is rendered according to the settings entered in the Preferences tab.
  12. You're done!
  13. Make a cup of your favorite hot beverage
  14. Open the audio package in your software media player. Sit back and listen to your completed magnum opus.
  15. Start thinking about a topic for your next podcast, which will be even better than this one!

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