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Audacity

Instructions:

2. Put the headset on.

3. Make sure that Mic Volume or Microphone is selected in the drop-down list at the top of the window.

4. Click the red Record button and begin speaking. A wave form will appear.

***IMPORTANT NOTE: If you want to stop speaking momentarily, click the Pause button rather than the Stop button. When you are ready to resume, click the Pause button again. If you do not use the Pause button when stopping and starting, you will wind up with many different tracks instead of one continuous track.***

5. Click the Stop button when you are finished. You cannot save the file if it is paused rather than stopped.

6. From the File menu, choose Export….

Choose a location for your file (such as the Desktop or My Documents folder), give your file a name with no spaces or special characters (i.e. lastname_date.mp3) and click Save.

A progress bar will appear as follows:

When you close Audacity, a Save changes before closing? prompt will appear. You should choose No, because you have already exported the file as MP3. This is somewhat confusing due to the way Audacity differentiates between saving and exporting.

Download Audacity for free at http://audacity.sourceforge.net.

File size / length ratio of audio files

The most common audio files used in the language labs are MP3 files and WAV files. There is a tremendous difference in file size between these two formats; WAV files are completely uncompressed while MP3 files have very good compression. For example, the table below shows the differences in file sizes of various audio files:

As you can see, WAV files are roughly seven times larger than MP3 files (at a bit rate of 96). The bit rate can be adjusted when exporting MP3 files. A higher bit rate means higher audio quality and larger file size. A lower bit rate means lower audio quality and smaller file size. By default, the bit rate is set on the language lab computers to 128.

File size of audio files and Blackboard

Blackboard has a file size limit of 25 MB per file or 100 MB for DDI (Duke Digital Initiative) courses. If your file is larger than your Blackboard course allows, you will not be able to upload it.

If you have a WAV file that is too large, you can convert it to MP3 format using Audacity or iTunes.

If you have an MP3 file that is too large, you can try re-exporting it at a different bit rate with Audacity. Should you need to adjust the bit rate, follow these steps:

1. In Audacity, choose Preferences… from the Edit menu.
2. Select File Formats in the list at the left.
3. Make your choice from the drop-down list for Bit Rate. Lower bit rate numbers will result in smaller file size but also lower sound quality. Higher bit rate numbers will result in better sound quality but larger file sizes.

The table below shows the lengths of a recording, using the various bit rates in the recommended range, which will result in a file size of just under 25 MB and just under 100 MB. If you need to record a longer speech sample and upload it into Blackboard, you can adjust the bit rate accordingly. Alternately, you could separate the recording into sections and save each section as a separate file.