Sound field studies of truck tires

To understand the noise source mechanism of tire/road noise better than in the past, it is essential to look at the complete sound field of a tire. In the technique of spatial transformation of sound fields (STSF), the Helmholtz integral equation is combined with the acoustical near‐field holography. Thus it is possible to analyze the noise source in great detail and to calculate the sound in the far field. A drawback of the acoustical holography is that only planar views of the sound field can be calculated. One method to overcome this limitation is to combine the measurement results of STSF with the inverse boundary element method. By modeling the surface of the tire with boundary elements, the velocities on each element can be identified. First results will be presented. Comparing the sound field of a standing tire excited by a shaker with the sound field of a tire on a drum, it is possible to extract the part of the sound field that is caused by the geometry on the tire only.