A tire noise reducing system comprises a pneumatic tire, a wheel rim and a noise damper disposed in a cavity formed between the rim and tire when mounted as being surrounded by the tire and rim, the noise damper is made of a porous material having a specific gravity of from 0.005 to 0.06 and secured on a surface facing the cavity, the volume S2 of the noise damper is in a range of from 0.4 to 20.0% of the volume S1 of the cavity. Preferably, the noise damper is provided with an uneven surface or an outer layer for less sound reflection, and the shape index E of the noise damper is more than 1, and the ratio T/W of the thickness T to the width W of the damper is not less than 1.