{HEAD ~ The piezoelectric pick up element} is situated in {TAIL ~ a casing}, said casing being fixed to a hollow body being tested as by a strap encompassing at least partly both the casing and the tested hollow body 
is situated in
{ HEAD ~ The piezoelectric pick up element } is situated in { TAIL ~ a casing } , said casing being fixed to a hollow body being tested as by a strap encompassing at least partly both the casing and the tested hollow body
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH