A tire noise reducing system comprises a wheel rim, a pneumatic tire to be mounted on the wheel rim and a noise damper to be disposed in an annular tire cavity enclosed by the wheel rim and the pneumatic tire mounted thereon, wherein the noise damper is made of a multi-cellular material whose volume S2 is in a range of not less than 0.4% of the volume S1 of said annular tire cavity. Preferably, the specific gravity of the damper is set in a range of from 0.005 to 0.06.