A flexible diaphragm situated in {TAIL ~ a rigid shell} affixed over an opening in the element wall divides {HEAD ~ the shell interior} into first and second variable volume chambers 
A flexible diaphragm situated in { TAIL ~ a rigid shell } affixed over an opening in the element wall divides { HEAD ~ the shell interior } into first and second variable volume chambers
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH