In a pneumatic tire, one of causes for generating noise is cavity resonance noise resulting from vibration of air filled in the tire. This cavity resonance noise is generated due to the vibration of air inside the tire, the vibration being caused by a tread portion vibrating due to irregularities of a road surface, when the tire is rolled.
As a method of reducing noise caused by a cavity resonance phenomenon as described above, it has been proposed that a time period during which resonance occurs at a single resonance frequency is reduced by having cross-sectional areas of a cavity portion, which is formed between a tire and a rim of a wheel, varied in a tire circumferential direction (for example, refer to Patent Document 1). Furthermore, in order to realize variations in cross-sectional area of the cavity portion at regular intervals, it has been proposed that a plurality of objects are mounted on an inner surface of the tire by using an annular jig (for example, refer to Patent Document 2).
In the above methods, however, the plurality of objects have to be arranged in locations facing each other inside the cavity portion, and therefore, it is difficult to even a weight balance of the tire in the tire circumferential direction. As a result, there is a problem that uniformity of the pneumatic tire is deteriorated.
[Patent Document 1] Japanese patent application Kokai publication No. 2001-113902
[Patent Document 2] Japanese patent application Kokai publication No. 2003-226104