Why can't I hear the sound files in Acrobat Reader on the iPad?

I have created on my main computer pdf files with embedded sound files. When I transfer them into the Adobe Reader on the iPad, the icons are there, but there is no sound. The only option Acrobat Pro XI has is to accept AIFF files. Whereas the guide for Adobe Reader on iPad says that it won't accept AIFF files, only some others, e.g., mp3.

Reuven