This paper presents a study of the acoustic radiation from a stationary brake system that was conducted in order to better understand the acoustic radiation from squealing brake systems. A large class of squeal mechanisms are associated with the resonant behavior of an operating brake system. In this work, an analysis is presented that equates the natural frequencies and modes of a mechanically-excited stationary brake system to those of an operating brake system. The equivalence allows one to conduct experiments on stationary brake systems in order to gain insight into the acoustic radiation mechanisms of squealing systems, which is a substantial convenience given the difficulty of artificially inducing squeal. The methodology is applied to scanning LDV measurements of the normal velocity of a shaker-excited stationary brake system. Acoustic radiation efficiencies and intensities of the modes were computed by importing the experimentally measured velocities into a BEM software package. These efficiencies approach unity at a coincidence frequency defined by comparing acoustic wavelengths to the wavelengths of flexural waves that propagate circumferentially around the rotor. For the particular system tested, this remarkably high radiation efficiency occurred at frequencies above 2–3 kHz.

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