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The dynamic material properties of viscoelastic materials are known to be sensitive to a variety of environmental factors. A great deal of attention has been given to characterization of the effects of temperature and frequency. However, for thorough design of some noise control schemes, such as isolation systems and tuned damper devices, it is often necessary to characterize the properties of viscoelastic materials as a function of dynamic strain amplitude and static prestrain, as well as temperature and frequency. Included is a description of test techniques utilized to characterize these properties, presentation of sample properties, and discussion of the applicability of the data to the design of noise control systems.

Considerable effort has been directed at investigation and reduction of brake noise. Most of this work has been performed on problem brake systems whose designs are finalized. Consequently, add-on noise control treatments have become a very common technique in eliminating the noise problems. The application of these treatments is sometimes regarded as a “cut and paste” or “trial and error” procedure where the effects of a huge matrix of noise control treatments is evaluated on a structure experimentally. In contrast, the design of effective noise control modifications can be achieved efficiently using existing measurement and design techniques. The initial approach is aimed at defining the dynamic characteristics of the brake system to identify the source and mechanism of the objectionable noise emissions. Successive work addresses the design, development, and performance verification of treatments or modifications applied to the system that can be used to control the noise.