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