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