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Patterned tires can not be build that are less than 1-3 dB(A) louder than smooth tires. Further reduction of tire excitation by tread pattern optimization cannot be expected. For further lowering the tire/road noise the tire construction and the excitation by road needs to be addressed. In the EC funded project SILENCE a subproject looks for further reduction possibilities of tire/road noise. For a straightforward improvement of tire/road noise the vibration pattern on the surface of a rolling tire must be known. In the project the tire vibrations of rolling tires were identified with indirect methods. Two new approaches will be presented in the paper: The framework for numerical optimization of point source positions and source strengths has been tested on a real tire rolling at 80 km/h. Models with one two to six sources have been produced, covering frequencies up to 1 kHz.

To understand the NVH mechanism of tire/road noise better than in the past, it is essential to look at the complete sound and vibration field around a tire. Regarding this challenge measurements with a microphone array were performed in the time domain at different speeds, different loads and different inflation pressures. In this paper first results from the measurements and the calculations for a blank tire are presented. Results from a modal analysis are compared with vibration calculation from sound field measurements around a standing tire excited by a shaker and it is shown how the vibrations are changed when the tire is rolling. The measured signals were used as input for an Inverse Boundary Element Method (IBEM) calculation of the tire vibration for both non-rolling and rolling. The outer surface of the loaded tire for the IBEM was calculated with in-house FEM software. The IBEM model also incorporates the test rig surface.

Localization and ranking of sound radiating regions on tyres under transient conditions is very difficult both because of the transient nature and because it is difficult to measure sufficiently close to the sound radiating regions. Using Near-field Acoustic Holography it is possible to measure at some distance and then extrapolate back to the surface of the tyre. With the Time Domain Acoustical Holography it is further possible to study the transient nature of the sound generation in any desired detail. As an example, the present paper compares the sound radiation under stationary and under accelerating conditions.