Extract audio files from powerpoint

Save your .ppt or .pptx file as "web page" (.htm,.html) with a new name. PowerPoint will create a file with the new file name, and an .htm extension. It will also create a new folder, called yourfilename_files, containing all the embedded objects including sounds in your presentation. Open this newly created folder and you will see all the audio files listed. If your file is in .pptx format, you can also rename it as filename.pptx.zip and you can browse the sound and image files inside the zip file.

Edit: For Mac, you can use File Juicer to extract sounds from your PowerPoint file. See the relevant page for more info.

Use this method without resorting to 3rd-party software:

Duplicate the .pptx file and change the extension to zip.

Unzip the resulting file. You'll see 3 folders and an .xml file.

Open the ppt folder to see more subfolders.

Look in the media folder.

Voilá!