It is well known that a tire’s fundamental air-cavity mode, typically near 200 Hz for current passenger car tires, can split into two adjacent features when a tire is loaded and hence deformed, thus creating a fore-aft, horizontal mode and a vertical mode. This split happens because the deformed tires is no longer geometrically symmetric: the air channel in the bottom region of the tire is narrowed, hence effectively increasing the inertia in that region, and thus causing the fore-aft mode, which has a relatively large particle velocity in the bottom part of the tire, to have a lower natural frequency than the vertical mode. These modes are important because they can create dynamic force inputs to the suspension system and thus they can contribute to vehicle interior noise at the modal natural frequencies. In the present work, measurements of the dispersion relations for a set of loaded tires was conducted to determine the range of magnitudes of the modal frequency split. Splits ranging from 3.4 Hz to 12 Hz at rated load have been identified, and it has also been found that the magnitude of the frequency split for a given tire is very nearly quadratically proportional to the applied load.
Tire noise. Acoustic cavity mode, Loaded tire, Frequency split, Measurements of dispersion relations
Acoustics and Noise Control
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