Then an analysis on the states of {TAIL ~ the M last 20ms blocks} allows the final decision on {HEAD ~ voice presence} 
Then an analysis on the states of { TAIL ~ the M last 20ms blocks } allows the final decision on { HEAD ~ voice presence }
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD