Caskey 3 Barlage (1971) used a vertical oscillating jet and directly measured the wavelength characteristics with a Gaertner two-coordinate cathe-
tometer . Instead of the usual drawn glass tubing for the orifice, they con- structed the orifice from 2 .0 mil Mylar film coated on both sides with paraf- fin. The Mylar film was attached to a Parker tubing nut to form the diaphragm orifice .