Speex dev - Aug 2004 - speex_denoise on non-microphone noise (static ?)

The problem started with speech detection.  Speech sections are detected
well.   However, once in a while non-speech sections are also marked as
speech.  The root was finally traced down to microphone static noise.

 

Then I pulled the microphone out. Our system still records noise.  To
isolate the problem, I wrote a small app just to open the device and
record raw samples, calls speex_denoise() and outputs both sample sets.
The noise is still there, with level fluctuating with gain level, unless
"All mute" is chosen.  

 

In the case when NO microphone is plugged in, speex_denoise() smoothes
the signal and produces smoother (and even amplifies the signal) speech
like signals.  It seems that speex_denoise( ) is very sensitive to
static noise.

 

For regular speech COMBINED with microphone static (or more precisely,
the static detected at the microphone plug, or noise from inside the PC
... someone help me out here), the noise samples do get suppressed
compared to speech samples. 

 

One observation: many noise sequences seem to have a signature of sharp
spikes.

 

Anyone have a solution of supressing this type of static?

 

Thank you.

 

 

 

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