Sonic and Sega All-Stars Racing .str and .was by Sora3087 at 5:21 PM EST on February 24, 2010
so the .str files from the 360 version look like they have a WAV header but it doesn't play and the .was from the wii version have 'SWS' in the header.
this is the same audio file from both games http://www.mediafire.com/?zmntdzzqijm
Most Plain XMA files are plain headerless but it is easy to see the beginning of the xma stream after the custom header. custom headers you can usually get the rate and channel number which is why it is useful to read it before you delete it and append your own.