[Error] DM6467 capture sound has noise

Hi All:

    I use default encode demo in latest DVSDK and the speech encode doesn't output good sound, then i change the speech.c to save the raw pcm data and find the pcm data with sharp noise.  is it a bug of the SDK or linux kernel ?

    My Test Environment:

          1 Hardware: DM6467 EVM

          2 Software : DVSDK_3_10_00 3_10_00_19  (Include all component needed,  it can get from http://software-dl.ti.com/dsps/dsps_public_sw/sdo_sb/targetcontent/dvsdk/DVSDK_3_10/latest/index_FDS.html)

         3 My test just capture sound (without video capture and encode);