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. The results with two sources have been found to agree well with existing knowledge of simple tire point source modeling. Results have shown that special emphasis on accuracy in certain frequency bands may be controlled by proper optimization cost function weighting.
A framework for time-domain Inverse Boundary Element Modeling (IBEM) has been established. Source-to-receiver transfer functions are determined by BEM and equivalent inverse time-domain filters are derived from these. Pressure time signals recorded near the rolling tire surface are then fed through the inverse filters to reconstruct the source surface velocity time signals. Animations indicate that moving mode shapes may be identified on the running tire.
