Team seeks tyre noise reduction

By Alison Ayres

It could lead to recommendations for improving the noise performance of Europe's roads.

European engineers are attempting to reduce the noise produced by car tyres.

Now that engines are quieter, the sound made by the wheels on the road accounts for most of the noise made by a vehicle doing more than 30 km/h (19 mph).

A team at Southampton's Institute of Sound and Vibration Research is working up a complete mathematical model of the way a car tyre produces sound.

The researchers will investigate whether subtle changes in the design of rubber tyres could damp down noise.

UK team leader Dr Roger Pinnington thinks this area of research has been sadly neglected.

He said: "We all accept traffic noise in cities and towns because it is continuous, but it would be very pleasant if it stopped."

Surface grip

As a car is moving, the roughness of the road surface causes the tyres to vibrate producing sound waves. This phenomenon causes a noise described as a roar or a rumble.

But making roads smoother is not the answer because another phenomenon occurs in which air is trapped by the advancing tyre. When it is forced out of the way it causes a noisy "shhhh" or hiss in a process called air-pumping.

Dr Pinnington is part of Ratin (Road and Tyre Interaction Noise), one of the first EC-funded projects to investigate and reduce tyre noise.

A new directive from Brussels means that by 2007 every car sold in Europe will undergo a sound trial in which specific attention will be paid to the noise coming from the tyres.

However, Dr Pinnington believes greater overall noise reduction could be achieved by changing the nature of road surfaces.

He explained: "A smoother road is generally quieter than a rough one, but it can be slippery when wet. New research shows that surfaces can be made that are both smooth and porous to water so I suspect this is the direction we may go in."

The project is a collaboration between the University of Southampton and the Aristotle University of Thessaloniki, Greece.