Strange sounds when encoding at 64kbps.
When encoding at quality level 0 there is a strange sound that appears in the background. It sounds sort of like the sound you would get using an older format such as MP3 at a low bitrate. At lower quality settings (-1), this problem does not exist.
The problem is specific to Vorbis and does not exist in the AAC encoder of iTunes, Windoze Media, or any other competing codec (Although those codecs do have bugs of their own...).
The song I found it in first was Burnout by Green Day. Also, I am listening on headphones.