Speex dev - May 2011 - decode wav file sounds noise but no when play the encode file

I test the speex codec effect  int the version of 1.2rc1.
Encode a wav file which sample rate equal 44100  the command line like this:
speexenc.exe --ultra-wideband --bitrate  20000 test.wav test.ogg
 I play test.ogg in windows media player,  it sounds acceptable.( I have install
the decoder oggcodecs_0.83.17220-win32.exe.)
After that decode test.ogg:
speexdec.exe test.ogg test_dec.wav
when I play test_dec.wav it sounds noise in that .bad than play the ogg file in
windows media player.
I use the command line the hear directly:
speexdec.exe test.ogg
It sounds like playing test_dec.wav with noise in that.
Can anyone tell me why  windows media player the ogg file (encode file) sounds
better than play the decoder wav file?
 
 
 
 

 
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