Insert Oscilloscope Meter-(Cockos) Fx
capture highest amplitude of quiet parts in Oscilloscope
Drag mouse on hold to freeze Oscilloscope
increase the range until you see the quiet parts
then left mouse drag the wave form in Oscilloscope to find the highest spot
read the value for example -21db
run Auto trim
set the threshold to that value (in this case -21db)
set ignore silence 2000 ms (which is 2 second)
it means cut everything below -21db if the duration of quiet parts is longer than 2 second.