Editing a digital voice recording: 2: Editing in Audacity

June 1, 2008

Once I’d successfully imported the converted WAV file in to Audacity, it was time to do File > Save As to make a copy then to start editing the copy. Some of the things I needed to do were:

  • Remove as much background noise as possible (see Scott Nesbitt’s excellent article “Cleaning up audio files with Audacity” for how to do this using Effect > Noise Removal).
  • Remove the “um’s and ah’s” and unrequired silences as far as possible without detracting from the ‘personality’ of the presentation. (Select the piece of the waveform you don’t want, then click the DEL key to delete it.)
  • Add silence where it was needed (Generate > Silence).
  • Add a tone to tell the listener to go to the next slide if they are viewing the slide presentation at the same time as listening to the audio (Generate > Tone; I used these settings: Waveform: Sine; Frequency: 440.00; Amplitude: 0.25; Seconds: 0.25)
  • Reduce the file size by changing the settings (drop-down arrow next to the track title in the summary box on the left). The settings I chose were 16-bit, 8000 Hz, Mono. With these settings I went from an original size of 75 MB to 62 MB, but with my editing I had also reduced the time from 75 mins to around 65 mins, so I’m not sure I saved anything; it looked as though about 1 min of voice is about 1 MB of file size.
  • Still looking for a smaller file size, I also found I could change my MP3 output bit rate preferences from 128 to 64 (Edit > Preferences > File Formats tab) – this reduced the file size to 31 MB with no apparent loss of voice quality (remember, this wasn’t a super good recording in the first place).
  • Save the file as a WAV file and an MP3, as well as save the project (AUP file format).
  • Add metadata (complete the ID3 tags as fully as possible when you save the file; I selected Speech as the genre).

All this required a lot of testing: zoom in, play, stop, rewind, play, test, etc. It probably took me some five hours to edit the 75 min presentation. Remember, I am totally new to this. Now that I’ve written down these instructions, I’d hope to be much quicker if I have to do this sort of thing again.

[Links last checked August 2012]

One comment

  1. It really bites that your DVR doesn’t export files that can be imported directly as WAV. A lot of it has to do with the file headers. What DVR do you have?

    Another great tool to apply after you remove the noise, but before you downsample the file, is the Levalator by the Conversations Network. It was designed for podcasters and does a great job “levelating” the voices of multiple speakers, or of different takes of the same speaker.

    Depending on your use, I would recommend against downsampling the file in Audacity before exporting to MP3. If you followed the instructions to install the LAME DLL into Audacity you can control the downsampling and audio quality when you export the final MP3.

    If you are planning to import the file into Flash, Camtasia, Captivate, etc., it’s best to import the full 16-bit/44.1kHz WAV format and let the host application manage the downsampling, for optimum quality.

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