Noise level is one of the key factors affecting driving comfort. As the popularity of quiet electric cars increases, more and more drivers have taken an interest in tyre noise, for example. External rolling noise and interior noise are different things, but you can reduce both by keeping your car and tyres in good condition. Nokian Tyres considers the noise aspect carefully in R&D and testing.
As consumers shop for new tyres, it is very difficult to know which of the available options would be the quietest on their vehicle. Tyre noise is affected by several factors, such as the model and type of the vehicle, the rims, rubber compound, road, driving speed, and even the weather. There are even differences between similar cars, making exact comparisons only possible in situations where the same car is used under identical conditions.
Some general assumptions can be made, however: The softer the tyre’s tread compound, the more it is likely to reduce noise. High-profile tyres are also generally more comfortable and quiet to drive than low-profile alternatives.
Summer and winter tyres have the EU tyre label that indicates the noise level. This label, however, only covers external rolling noise. External rolling noise and interior noise may even be polar opposites, and reducing one may increase the other.
“What you hear inside the vehicle is a combination of many things. Tyre noise originates from the tyre’s contact with the road: roughness causes the tyre body to vibrate as the tyre rolls over it. From there, the vibration travels a long distance through the tyre, rim, and other vehicle structures into the passenger compartment, where some of it turns into audible sound”, says Senior Development Engineer Hannu Onnela from Nokian Tyres.
Tests require gauges and human ears
So far, Nokian Tyres has been performing noise tests on its track located in Nokia. The new testing centre completed in Santa Cruz de la Zarza, Spain has a 1.9-kilometer “comfort road” track that offers even better testing opportunities than before. The facilities in Spain allow for testing tyres on different types of asphalt and rough roads, as well as crossing cobblestone streets.
“The gauges do not tell us everything that we need to know, so we also perform a lot of subjective testing based on human assessment. It is important to find out if a noise is disturbing, even if a gauge cannot detect it”, Hannu Onnela explains.
Tyre design always means finding the best possible compromise. Changing one characteristic will also alter the others in some manner. Safety is the number one priority, but developers also try to fine-tune the other characteristics for the best possible result.
“Products for different markets emphasise different features. The CE winter tyres are quieter than summer ones. Although Nordic winter tyres tend to be the quietest tyres because of even thicker tread and softer tread compound than CE winter tyres have. The tyre’s interior noise characteristics are emphasised when the car is commonly used at speeds of 50–100 km/h”, says Head of R&D Olli Seppälä.
Even wear reduces tyre noise
As the tyre change season is ahead of us, drivers should note that changing the tyres makes us sensitive to noise. Old tyres also have low tread depth, which creates a different soundscape than new tyres with their strong tread patterns.
Drivers can affect tyre noise to some extent. First, you should make sure that your car and tyres are fine. For example, if your suspension geometry is not within the manufacturer’s specifications, resulting in incorrect steering angles, the tyres will wear down unevenly and generate additional noise. Even if your wheels are properly aligned, you should rotate your tyres in order for them to wear down as evenly as possible.
