Everyone wants a car that doesn’t make any sound as it goes down the road. Unfortunately, no one can beat the laws of physics and therefore, all tyres generate noise while rolling on the surface. The air that flows between the tread and tread blocks that go in and out of contact with the road are the main culprits behind tyre noise.
The engineers have a real challenge in front of them to balance tread noise with traction. This is the reason why off-road tyres are noisier compared to the mild-tread tyres that are quieter but fail to perform in off-road conditions.
It is not always on tyres though. You must have noticed several times that as the car drives from concrete surface to asphalt, the tyre sound changes. The truest test of tread pattern noise should be done on the quiet surfaces like new asphalt roads. It is possible that after changing to new tyres, the tread noise does not change. In this case, the noise is most likely due to the surface the car is running on.
What is pitch and how does it effect tyre noise?
Tyre developers generally use the term pitch to describe the number of tread blocks on the circumference of the tyre. It is usually observed that performance tyres have bigger but fewer tread blocks and off-road/winter tyres have smaller, more tread blocks, i.e. the pitch of performance tyres is less than off-road tyres.
As discussed above, off-road tyres are noisier when compared to performance tyres. The positioning and shape of tread blocks also greatly impact on the tyre noise. Engineers try to create different pitch sizes on a tyre. This is done because if every tread block on the tyre is of same shape and size then all of them will generate almost similar sound frequency and the same kind of sound tone from each tread block will add up to create lots of noise when the tyre is in motion. Tyre designers use computers to sequence multi-pitch tread design to randomise the shape and size of tread block to offset the sound frequency generated from the tyres.