Precision ultrasonic reflection studies in fluid‐coupled plates

An approximate, but highly accurate, analysis is presented for the reflection of bounded acoustic beams—and their detection by finite receivers—from fluid‐loaded structures, demonstrating the relationship between the plane‐wave reflection coefficient and the transducer voltage. The correspondence of the reflection coefficient zeros, in both angle and frequency, with the observed voltage minima is found to depend critically on the experimental geometry, especially the lateral transducer placement. In measurements with two identical transducers, the beam shape, its sidelobes, and far‐field or near‐field conditions are found to play a relatively minor role in the receiver voltage. Instead, the size of the transducers and their relative lateral positioning with respect to the sample are the major geometrical factors determining the appearance, width, and depth of reflection minima. A series of precision, swept‐frequency experiments on a uniform, homogeneous plate to validate the calculation and expose any pos...