Speex dev - Jul 2006 - RE: Preprocessor VAD failure

I am using the Speex preprocessor in 1.1.12 and found that its VAD may
not detect some speech. I have attached the .wav file I used. Sample
format is 16 bit little endian PCM, 8k narrow band. I used default
setting and only enabled Denoise VAD. My test speech does have some
background noise, and the Denoise feature works very well, but VAD says
all the frames are silent. Does anyone know why? I can send my test
audio file upon request. Thanks.

   st = speex_preprocess_state_init(160, 8000);
   i=1;
   speex_preprocess_ctl(st, SPEEX_PREPROCESS_SET_DENOISE, &i);
   speex_preprocess_ctl(st, SPEEX_PREPROCESS_SET_VAD, &i);
   i=0;
   speex_preprocess_ctl(st, SPEEX_PREPROCESS_SET_AGC, &i);
   ...
   vad = speex_preprocess(st, frameIn, NULL);


Yi

In the preprocessor, why is VAD done before denoising? If denoising is
done first, VAD will work more correctly without the noise; otherwise,
VAD may not detect all speech frames.