You should be able to upload your audio/video into the file manager, if upload and course quota size limit allow it, then when creating question use the Insert function in the popup file manager to insert a link to the file into the question.
Or, you could try uing the EMBED element to prevload the audio/video, something like the following. You will need to adjust the value of src, either pointing the link directly to the files in your file manager if the content/ directory is within your ATutor installation, or using get.php to represent the path to the files if your content/ directory is outside your ATutor installation.
<embed src="/content/8/my_start_page.mp3" autostart="false" hidden="true" volumn="8" name="my_start_page">
or
<embed src="/get.php/my_start_page.mp3" autostart="false" hidden="true" volumn="8" name="my_start_page">
You could also use the OBJECT element to embed the audio/video in your test questions.
Search the web for different examples of EMBED and OBJECT.
OBJECT
http://www.htmlhelp.com/reference/html40/special/object.html