Dear Luke,
I tried many combination of parameters about "audioconvet" and even "audioresample" to other frequency.
It did not work.
I can found that noise is gone after 8K frequency re-sampling, but quality is bad.
gst-launch filesrc location=africa-toto.wav ! wavparse ! queue ! audioconvert ! alsasink
gst-launch filesrc location=audio.wav ! decodebin ! audioconvert ! audioresample ! audio/x-raw-int,rate=44100 ! alsasink
Thank you.