Tire noise reducing system

A tire noise reducing system comprises a wheel rim (2), a pneumatic tire (3) and a noise damper (4) disposed in the tire cavity and made from a spongy material whose total volume is in a range of from 0.4 to 20 % of a volume of the tire cavity. The maximum thickness (t) of the damper between the base end surface (4A) and the top end surface (4B) is in a range of from 1.0 to 4.5 cm. The width (W1) of the base end surface is more than the maximum thickness (t). The width of the damper is not increased in the direction from the base end surface (4A) to the top end surface (4B), and each of side faces (4C) defined as extending from the edges of the base end surface (4A) to the edges of the top end surface (4B) is at least partially provided with an aslant portion (10) inclined at an angle theta of from 30 to 75 degrees with respect to the base end surface (4A). The damper (4) is preferably fixed to the inside of a tread portion (3t) of the tire (3).