Tires for vehicles have various tread patterns, usually to balance the amount of traction to the road surface during dry and wet weather. As most people know, a solid soft tyre has the greatest surface area in contact with the road and hence has the most amount of traction. The tread pattern allows water to escape when the tire is on wet roads.
When the tread is in contact with the road surface, volumes of air are formed between the road and the tread pattern in the tire, which is compressed as the tire rotates. The volumes of air are a network of small Helmholtz resonators that generate noise.
In addition, the interaction of the tread pattern with the road vibrates the body of the tire and causes the walls of the tire to radiate noise.
Read an article on tire noise by Stuart Bolton.