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Applications of ultrasonic techniques in non-destructive evaluation have evolved from detection and imaging to quantitative characterization. As discussed in this lecture, a typical example is the quantitative mode of line-focus acoustic microscopy, which has become a very useful technique for the determination of surface wave speeds and thereby the elastic constants of an anisotropic thin film deposited on an anisotropic elastic substrate. The determination of these constants is generally based on the measurement of the V(z) curve, which is the record of the modulus of the measured voltage at the transducer as a function of the distance z between the focus of the lens and the surface of the specimen. The procedure has three essential components: 1) the measurement of the V(z) curve, 2) the development of a theoretical measurement model for parametric studies of V(z) curves, and 3) a procedure to obtain the elastic constants by systematic comparison of wave mode velocities obtained from the theoretical model and the V(z) measurements. Examples are presented for thin protective coatings. Sensitivity of the technique and accuracy of the results are briefly discussed.