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I recently wrote an HTML5 audio player. I had similar trouble with iOS4 and iOS5. First, the play has to be triggered by user input, meaning specifically that it has to be in the same call stack as a click event.

I tested this a lot, and iOS seemed to refuse to cache the audio at all. It fetched the audio with every play. I think this should be considered a bug, but perhaps they are trying to preserve local storage space (audio files can get rather large).

If your audio files are not too large, you might want to consider appending them together into a single file and then using pause / jump to position / play to switch between sounds. I haven't tried it, but it should work. I didn't use the technique because my app was a music player, and music files are a bit too large for that technique to be valuable.

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