Are there any notoriously bad Ogg Vorbis encoders?
I am wondering because I have noticed a particular disturbing artifact on many Spotify tracks. What could cause this?  I'd like to reproduce this sound in order to back up my suspicions. I can't seem to reproduce the noise no matter how low quality I compress my test audio, so my first guess was that Spotify could have used a bad encoder, earlier version, etc. Much like some early MP3 encoders, such as Xing, were notorious for producing poor quality MP3s.

I have some samples available on my blog:

http://www.mattmontag.com/music/weird-spotify-compression-artifacts
Are there any notoriously bad Ogg Vorbis encoders?
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I am wondering because I have noticed a particular disturbing artifact on many Spotify tracks. What could cause this?  I'd like to reproduce this sound in order to back up my suspicions. I can't seem to reproduce the noise no matter how low quality I compress my test audio, so my first guess was that Spotify could have used a bad encoder, earlier version, etc. Much like some early MP3 encoders, such as Xing, were notorious for producing poor quality MP3s.

I have some samples available on my blog:

http://www.mattmontag.com/music/weird-spotify-compression-artifacts