Here is the documentation from the HTML5 audio library I use:
NOTE: In order to save bandwidth, mobile devices don't load/play sounds without user intervention (no autoplay). iPhone and iPad can only play one sound at a time and don't allow to change the volume dynamically. iPad has some issues with multiple sounds on the same page.
... and I use .wav files, which the Android stock browser may not be so hot at parsing -- but Chrome should be fine.
