Abstract: When an ultrasonic transducer for detecting discontinuities and/or delaminations in a thin layer of coated material applied to a metal plate or the outside wall or surface of a cast iron dryer cylinder is directed at the coated surface to be inspected at a particular angle, about 10 percent of the single will appear as Harris waves which propagate into the coated test plate at 90 degrees to the surface. This signal which propagates vertically is polarized, with the result that the signal has a greatly improved signal-to-noise ratio. For incident medium of Lucite and employing shear wave refracting in the medium of Lucite, the specific angle is approximately 66 degrees from the vertical for best signal-to-noise ratio. Shear or longitudinal waves can be employed to affect the detection of subsurface defects with the particular angle changing depending on the relation of the velocity of the sound waves in the refracting medium to the velocity of sound waves in the incident medium.