Abstract

It is well-known that acoustical modes exist in tire cavities. Previous research on tire cavity modes has focused on the transmission of structure-borne noise to the vehicle interior due to the force that the tire cavity mode exerts on the wheel hub. In contrast, here the major concern is the identification of the tire surface vibration and the sound radiation from the tire surface that can be attributed to the tire cavity mode. The surface normal vibration of a point-driven tire has been measured over a complete circumference by using a scanning laser Doppler vibrometer. When the space-frequency data is transformed to the wave number-frequency domain, a clear feature that can be attributed to the tire cavity mode becomes visible. Although the magnitude of the surface vibration resulting from the tire cavity mode is small, its radiation efficiency is high owing to the high phase speed of the acoustical waves that create the tire cavity mode. It has also been found, that, as expected, tire vibration features associated with the tire cavity mode disappear when the tire is filled with fibrous, sound-absorbing material. Finally, measurements of sound radiation from a tire driven by a steady-state, point-input, and from a tire driven by a uniform impact over the contact patch area are presented, and the features associated with the tire cavity mode are highlighted.