As one of tire noises is known a so-called road noise which sounds like “GHO” within a frequency range of 50 to 400 Hz when running on a road. A main cause of the road noise is considered a resonance vibration of air (cavity resonance) which generates in the tire cavity. In recent years, a technology is proposed in which a noise damper which is made of a spongy material and extends circumferentially is fixed onto an inner surface of a tire to ease and absorb a resonance energy generated in the tire cavity, thereby suppressing the cavity resonance to reduce a road noise (see for example Patent Literature 1).
Patent Literature 1: JP-A-2003-63208
According to Patent Literature 1, the noise suppression performance has a strong correlation with a volume ratio V2/V1 of a volume V2 of the noise damper to a whole volume V1 of the tire cavity. It is disclosed that the noise suppression performance can be obtained by securing a certain value or more of the volume ratio V2/V1, and the circumferential length, width, thickness and so on of the noise damper are not particularly limited from the viewpoint of the noise suppression performance. However, if the noise damper is formed on a part of a tire in the circumferential direction, there arises a problem that the weight balance in the circumferential direction is impaired to cause deterioration of the tire uniformity even though the specific gravity of the spongy material is low.
Therefore, from the viewpoint of the uniformity, it is important to fix the noise damper over an approximately entire length of the tire in the circumferential direction. For this purpose, it is required to set the circumferential length of the noise damper depending on a tire size based on the circumferential length of the tire. In order to reduce a material cost by minimizing the use of a spongy material on the premise that the noise damper is fixed over approximately entire circumferential length of the tire, it is also required to set the sectional shape (sectional area) of the noise damper in detail depending on the tire size based on the sectional area of the tire cavity.
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