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Disc brake squeal is caused by mechanical vibrations generated from friction force excitations exerted by the pad on the rotor. In an effort to understand the origin of these vibrations and speed the design of quiet brakes, proper characterization of the individual brake system components is desirable. In this paper we apply modal analysis, combining both experimental and analytical methods to measure and model the pad and rotor assemblies and compare the results to those obtained on vehicle and noise dynamometer tests. Of particular importance, ultrasonic methods are used to measure the friction material elastic properties. The Young's moduli, shear moduli, and Poisson's ratios are essential for quantitative analytical modal analysis. We find that the friction materials are highly anisotropic. For example in some formulations we find more than a factor of five difference between the in-plane and out-of-plane Young's modulus.