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The simulated indoor pass-by noise measurement system is the measurement tool to evaluate the pass-by noise at the test laboratory, without doing measurement at the field. This measurement system can overcome the limitations of the field measurement, i.e. weather conditions, reproducibility. In this measurement, microphone array is located around the car on chassis dyno. The measured time-domain signals are synchronized with one signal, which is equivalent to the signal recorded in the field representing the moving source effect. By using FRF between indicator and receiver microphones, which are representing source strength and evaluation points correspondingly, source path contribution analysis is performed at 7.5m apart from the centerline of car. In this paper, the measurement and signal processing on top of the theoretical background would be discussed with the measurement example.

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.