Study on Tire Noise

Abstract

Today traffic noise is one of the major problems related to noise pollutions. It is increasing day by day with the increase in the number of vehicles on the road. The sources of noise from a vehicle can be separated into four main areas, the engine, exhaust exit, air intake and the noise produced as a result of the tires rolling in contact with the road surface. Reductions in the levels of noise from the former sources have been significant and it is now recognized that the tire/road interaction noise is dominant for constant speeds in almost all types of driving, certainly above 40 km/h for cars. For reducing the noise generation from tires and eliminating the ill effects caused by noise pollution to environment and society, noise produced form the tire/road interaction have to be studied carefully.  Tire/road noise is produced due to some generation mechanisms i.e mechanical, aerodynamical, frictional or propagational, when tire rolls over the road surface and these generation mechanisms depend upon some of the operating conditions like vehicle speed, tread pattern type, type of road surface, condition of tire etc. In this work, different types of tire noise generation mechanisms and different kind of measurement methods are discussed briefly.  More focus is on the effect of different operating parameters on tire/road noise.  For this, an experimental rig is fabricated. Background noise level is estimated first and then removed with the help of shielding being done by making a wooden box, a wooden wall having a layer of an absorbing material fixed, before taking the measurement.  Effect of vehicle speed, tread pattern design, road surface and tread wear on tire/road noise is examined. Three two-wheeler tires are used, named as A, B, C for studying the effect of tread pattern on sound pressure level. Four different speeds are used with the help of multiple pulleys attached to the motor shaft, for determining the effect of speed variation on sound pressure level. Two road surfaces, asphalt and concrete are prepared and different conditions i.e dry, wet, oily of each of them are taken for studying the effect of road surface conditions on sound pressure level.  For the whole work, two-wheeler tires are used. Close proximity method is used for taking the measurements. Measurements are taken at an angle of 45 degree to the leading edge having sound level meter (SC-310) placed at 4 inches above the level of tire/pavement contact and 8 inches away from the centre of tire. A-weighted sound pressure level (Leq) and 1-1 octave band frequency spectrum measurements are taken under the combined effect of different operating parameters.