Recording & Editing Audio

Audio Editing in Audacity - Basic

Audacity is compatable with Windows 98, ME, 2000, & XP, Mac OS9 and X, Linux, and Unix. To download the program go to the Audacity website.

  1. Before you start, go to your computer's sound control panel and make sure your input device (or your microphone) is selected as the audio input source. Then boot Audacity and go to preferences. Set the device(s) you are recording from and playing to in the audio I/O tab. If you are editing a pre-recorded file from your webcast for example, open Audacity then use the Import tool to open the pre-recorded file.The Quality tab sets the sample rate and bit depth. Jeff Towne from the Transcom Tools Content site says "Audacity can handle different sample rates and bit depths within a project, but these will be converted in real-time to the default session settings when needed. Although normally 16-bit is a sufficient bit-depth for webcasts, and you will save a good deal of disc space and processing power if you use that depth, Audacity sometimes creates grungy-sounding sound files when recording at 16 bit. I'd start with 16 bit, but if you have that problem, setting up your session to record at 32-bit float might solve it. Set that in the file format tab as the default export format." You can change the sample rate from the lower left corner also.

  2. Hit the red record circle in the transport panel to record. You can adjust the record level with the slider next to the microphone icon in the top right corner. You should leave it all the way up and change levels from your sound card or control panel. Make sure your input level does not go into the "red" (or hit the ceiling) on your meter as that will cause clipping. You can import audio into your Audacity project if you wish to combine more than one recording or add music etc. They will show up as new tracks.

  3. Editing tools -
    • the control toolbar is like any audio player transport buttons. Pressing the spacebar will start and stop play, and shift-spacebar will loop-play a selected section (called a region).

      Editing Tools
    • To select a section, click on the selector tool and drag over the part of the audio you want to change. Move the cursor over the edges of the highlighted section to grap and extend the length. Press Z to move the selection edges to zero-crossings eliminating clicks from edits.
    • For gain changes (also known as trim..it refers to the intensity of an audio signal), highlight a region (section) and use the "amplify" or "normalize" commands from the effect menu, or move the volume slider at the left of the track display. That slider sets the level for the track.
    • Use the draw tool like a pencil to re-draw waveforms to eliminate eliminate clicks or other distortions.
    • Click and drag over part of a track to zoom in. The magnifying-glass icons on the right hand side of the top of the track window can be used to zoom in or out in steps, to zoom to the selection, or to zoom out to see the entire project at once. A scroll wheel works as well.
    • Cut, Copy and Paste work as expected. Highlight audio you don't want and press delete. Audacity will close the gap. Audacity Editing tools
    • Use the silence selection tool (mute) if you'd like to remove audio without making changes to the timeline.Select audio you want to keep and click trim to selection to delete everything except the selected region. The silence selection icon mutes selected audio, but without moving any other audio regions, leaving a silent space, like hitting "mute" for that time range. Any other edits will close up that gap.
    • You can grab the vertical edges of a track and drag up or down to make it wider and easier to see for editing. The track can be reduced in size to see more tracks after you are finished editing
    • You can always undo edits, but not after you save. Audacity saves small ".aud" files that has all the editing data, so you can do multiple save-as steps to store different versions of the project, to retain flexibility without duplicating all the large sound files. Selecting view>history will show you a list of your actions, and by clicking on the various entries, the edits will revert to that stage of the edit, you can then discard all moves after that point by clicking the discard button. The history list is cleared whenever you save and you cannot undo after a save. Audacity has been known to crash, so save often.
    • You can use the Audacity plug-ins like the compressor, EQ, filters and normalizing. The Audacity "Noise Removal" effect is not the best and I don't recommend it. Audacity's effects need to be applied one at a time. To remove an effect, you have to step backward with "undo."

  4. Export selected parts of a project by highlighting them and choosing export selected from the file menu.

  5. Final MP3 - (for uploading into your blog) When you are done with the mixing and editing, (make sure your audio levels are high but not clipping) export your project by clicking File>Export As>an MP3. You may also Export as a WAV file or an Ogg Vorbis, another kind of compressed file. Just saving it will not make it a final mix. Be sure to us this Export tool so your final product can be uploaded to Webcast Academy, burned to CD or FTP'd.

  6. Learn Keyboard shortcuts for Audacity to speed up your editing time.

References

  • Information for this article is from The Transom Tools Content article by Jeff Towne
  • Level Headed ~ Jeff Towne
  • Processing Basics ~ Jeff Towne
  • Digital Editing Basics ~ Barrett Golding
  • AttachmentSize
    Image icon audedit.gif4.04 KB
    Image icon audtool.gif2.51 KB

    Worldbridges/Webcast Academy Audio Specifications

    Some degree of standardization in audio is necessary in order to maintain audio quality, functionality, organization, and  good overall cyber ecology.

    • All audio produced and uploaded on Worldbridges sites should be:|
      • an mp3 file encoded at no more than a 64kbs bitrate. Higher bitrate files can be exchanged as pre-edited raw files. 
      • Sample rate should be 22 or 44khz in order for the audio to work with audio flash players.
      Screencast: Configuring Audio Specifications in Audacity
    • ID3 tags should include the Title, Artist, website URL (in comments section), and Licensing information
      (creative commons licensing info)
      Screencast How to deal with ID3 tags
    • Filenames should always describe the content of audio, date produced, and be unique from any other filename. For example, intern introductions should be named like - jane-doe-introduction-2007-08-01.mp3
      Do NOT use spaces or special characters (i.e. # @ & $ !) in filenames. Underscores and dashes are fine.

    All About Compressors and Limiters

    What is a Compressor?

    A Compressor is a programmable gain(increase in signal strength or intensity) controller designed to decrease the difference in level between quiet and loud signals passing through it. The official definition is a programmable amplifier designed to decrease the difference in level between quiet and loud signals passing through it.

    What is a Limiter?

    A Limiter is a gain controller whose output goes so high but no further, and above a selectable point any increase in level at its input is not reflected in any increase in level at its output.

    How do they Relate to Each Other?

    These two functions are related, and can often come together. If dynamic range were a room then a compressor adjusts both the floor and the ceiling, and a limiter adjusts only the ceiling.

    Audio Editing

    Post-production audio editing takes place after each webcast and in some cases makes the difference between producing audio that this 'listenable' or not.