Study on the Directivity of Truck Radial Tire Noise

This paper experimentally and analytically investigate the directivity of truck radial tire noise. In the near field, it is well known that the tire noise demonstrate strong directivity. The characterization and modeling this directivity is important for engineers to understand tire noise mechanism and develop low noise tires. For truck radial tires, the directivity of the near field noise is not investigated adequately. Five truck radial tires with different patterns, i.e. block pattern, longitudinal rib pattern and hybrid paten, are tested in semi- anechoic chamber, to obtain their acoustic spectrum, under 4 speeds, 50, 70, 90, 120 km/h. A concept, acoustic roundness, is proposed to characterize the directivity for tire noise in all frequencies under all speeds. It can be found that the directivity depends on the tire frequency very much, while speed's influence on directivity is weak. A transition frequency can be found beyond which the extent of the directivity increase dramatically. The findings and conclusion in this paper are useful for tire engenderers understand tire noise generation mechanism.