How can I read an audio stream stored in a bean on the fly from a richfaces page with mediaOutput?

Here is the code:

<a4j:mediaOutput element="object" cacheable="false" id="audio"  
      createContent="#{myBean.play}"  
      mimeType="audio" />  

Bean:

public void play(OutputStream stream, Object data) throws Exception {  
    byte[] soundData = audioCaptcha.getChallenge().asByteArray();
    stream.write(soundData);
} 

Right now, I have a little grey div appearing in my page with the following message: "A plugin is needed to display this content".

Now, if I change the mimeType from "audio" to "audio/mpeg", I get the following error message in the grey div: "Video can't be played because the file is corrupt.".

Am I missing something? Or is there another way to achieve this?