Hi,
I suggest you refer to this link about the limit for video and audio in web:
You can play video and audio in Reading View and Slide Show if you have Silverlight installed. You’ll need Flash for videos that are linked from a website. Keep an eye on the file size, because PowerPoint for the web won’t insert large media files. For embedded media, the size limit can be from 50-100MB, and for WAV files the limit is 100KB.
Please check to see if the audio you insert exceeds these limits, just checking in to see if the information was helpful. Please let us know if you would like further assistance.
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