You can upload a voice recording but when you click on it in CaseWeb it will tell you that the file has not been found, however if you when you receive that message, click on the Tools cog in the bottom right hand of the screen, and then click on the green save button, it will save the recording to your device and it can then be played.
So in summary, yes you can save the file in CaseWeb but it will not play just by clicking on it, you would need to follow the instruction above.