From Assessment themes you can add, delete or change the names on static content, eg sound files. 

Click on the theme you want to add new static content to.

Then click on Static content. 

Already uploaded files are listed. Click Add element. 

Write the name of the file in upper case letters and with no spaces. You can use AUDIO, VIDEO or IMAGE. Upload the file by clicking on the speaker icon.

Browse for a file, or drop it in the box. 

Save the file by clicking Save to the right of the element you are working on. Note that a red speaker icon has no content, a black one has a file uploaded. 

You can listen to a file by clicking on the speaker icon again and clickin Play.