Influence of the cavity mode on tire surface vibration

Won Hong Choi, Purdue University

Abstract

As the technologies of vehicles have improved, the need for reducing tire noise is becoming more important. So far, there have been several studies on this subject. In general, forces at the contact patch cause essentially structure-borne waves to propagate along the tire carcass and essentially airborne waves to propagate within the tire cavity. Since these wave types are coupled, the airborne interior waves contribute to tire surface vibration and then exterior sound radiation. However, the effect of the air cavity on external sound radiation has not been studied as extensively as the sound radiation from structure-borne vibrations. In fact, detecting a tire cavity mode under various conditions has recently become more important because it may be possible to detect hazardous substances such as explosives in the tire cavity by measuring acoustic radiation from the tire cavity. Here the effect of the interior acoustic mode on tire surface vibration (and hence, on sound radiation) has been studied. To this end, a fully-coupled finite element model of an inflated tire consisting of a treadband, sidewall and an acoustical cavity has been constructed. That model has been used to study the spatial character of the interior acoustic field and to distinguish between components associated with sub-sonic tire carcass vibration and the interior acoustical modes. The influence of the spatial distribution of the input force (i.e., point versus patch) on the relative strengths of the acoustic and structural modes has also been examined. The influence of the interior acoustic field on the tire surface vibration has been isolated by using wave number transform techniques to identify surface vibration components matching the interior mode in shape and phase speed. To investigate the effect of deflection in the contact patch area on carcass vibration and the interior acoustical modes, a deformed tire was simulated using a finite element model. It was confirmed that deflection in the contact patch area leads to separation of otherwise degenerate acoustical modes (i.e., the fore-aft mode and the vertical mode). Finally, wave-number filtering was applied to visualize the tire surface vibration related to the interior acoustical mode. A simple longitudinal quadrupole model for radiation from the fundamental cavity model for a tire on a reflecting surface was then proposed and was successfully compared with experimental results.

Degree

M.S.E.

Advisors

BOLTON, Purdue University.

Subject Area

Mechanical engineering|Acoustics

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