I found the following question on the BSI Simian forum:
"I've been working on importing MP3s to our music library - transcoding infact (I know - aweful) - and I've noticed that sometimes SoundHound will not import an audio file - and even Info Editor will not open it. Both give an error that says "Bad Audio Data" - and I assume the problem lies with how the songs have been tagged.
What version of ID3 does Simian recognize? In the past, I've used mp3tag (www.mp3tag.de) to tag some songs - and afterwords, have recieved the error.
Does Simian recognized ID3v2 - and if so - is the format UTF-16 or ISO-8859-1?"
I've also noticed that the mp3 files that I've tagged (APE) with mp3tag give the same error. They contain additional information for StationPlaylist and mp3Gain. Could this be the reason?