Electric cars|Where does tire noise come from? An expert twists iron wire.
The summary is made by artificial intelligence and checked by a human.
The first versions of the Tesla Model 3 and -Y cars have received criticism for being noisy.
Mikko Liukkula of Nokian Tires explains that tire noise is not caused by the car’s driving force.
There are two types of tire noise: air-borne and structure-borne.
The silence of electric cars emphasizes the tire noise, but the weight and width of the tires can also have an effect.
Part Those who have driven the first versions of Tesla’s Model 3 and -Y cars have complained that the car is a bit noisy. For example, tire noise can be loud.
The same message has been heard from the mouths of other electric car drivers. Aren’t electric cars supposed to be wonderfully quiet?
Tire noise was one of the issues investigated by HS in a recent big winter tire test. Is loud tire noise specific to electric cars?
Expert gives a direct answer:
“No – tire noise has nothing to do with the car’s driving force,” says Nokian Tires’ development manager Mikko Liukkula.
He has worked in tire design for 22 years.
Then Liukkula explains what we’re talking about when we talk about tire noise – and why it might seem louder in electric cars than in combustion engine cars.
In HS’s winter tire test, studded tires were also tested on a wet surface.
Tire noise is of two kinds.
The first type of noise is air-borne tire noise. This type of noise dominates the soundscape at urban speeds.
The sounds that the tire makes when it touches the road, when the studs rust and so on are heard through the air.
When you go to highway speeds, the above-mentioned sound is no longer heard, because the sound world is dominated by the whistling of the wind and the tire sounds transmitted through the vehicle’s suspension and frame.
The noise caused by the air falls below the tire noise caused by the vehicle’s structures in the cockpit during fast driving.
Second the type of noise can be heard as humming and rumbling inside the car. The sound is caused by resonance: the air inside the tire vibrates at its characteristic frequency or the structure of the tire itself begins to resonate.
You can think of the air inside the tire as a donut that pulsates, collides and vibrates inside the tire. This resonance is carried along the car’s structures into the interior as a humming sound.
It may seem strange that the air collides in this way and causes vibrations, but the air inside the tire is really “hard”. It is often in the tire at a pressure of 2–3 bar.
“There are two frequency peaks between 200 and 250 hertz, which are the most annoying frequency range, which hinder conversation and disturb people,” says Liukkula.
Don’t forget to read HS’s recent tire test
HS tested six studded tires for the coming winter, you can read the results of the recent test here. In the fascinating test, the noise levels of the tires were also investigated. The test was run in harsh conditions with Tesla’s Model Y car, which was the best-selling electric car in the world based on sales figures.
There were tires from six manufacturers, including Nokia. The tire in question was not the quietest tire in the test, but the test group still found it pleasant in terms of sound.
This article and the tire test were written independently and at different times.
Usually the bigger the rims – i.e. the less rubber there is between the rim and the road – the louder the tire noise.
Tire wear also increases noise. The reason for this is illustrated by Liukkula with an example of an anasine.
If you cut a piece of the surface pattern of a worn tire, put it on an anvil and hit it with a hammer, the hammer will bounce into the air.
“That is, in a worn tire hysteresis – the way it absorbs energy – is almost non-existent.”
If you cut a piece of the new tire’s tread pattern, it will be thicker because there is more tread. If you hit this piece with a hammer, it will absorb the energy of the impact and the hammer will not pop much.
The new tire therefore “absorbs” into the road in the same way that the worn tire seems to bounce on the road. The latter causes resonance, which can be heard in the cabin as tire noise.
Tires tested by HS in a joint portrait, Michelin’s X-Ice North 4 in the middle.
To the tire patterning has a big effect on noise.
“With the right pattern, the periodic vibration frequency of the tire can be broken, which would otherwise excite the characteristic frequencies of the tire and cause noise.”
The noise is also affected by the poor condition of the road. This is a big problem in Finland, especially in spring, when the winter has disciplined the roads.
When the asphalt is worn, small bumps have formed on it, which awaken the resonance of the tire structure and the air inside. Liukkula advises you to always drive outside the ruts on the road, where the asphalt is smoother and does not cause so much tire noise.
For the same reason, studded tires are louder than friction tires. The studs awaken the resonance of the characteristic frequencies of the tire and the airspace, which produces sound at highway speeds.
At lower speeds, of course, the studs also cause tire noise caused by air when they rattle against the road.
Why some people seem to have the experience that the tire noise is especially loud in electric cars?
Liukkula believes that part of the reason may be in the quietness of electric cars: when there are no sounds from the engine, people notice the noise of the tires more easily. This is especially noticeable at lower speeds, where passing noise dominates the sound world.
In some cases, the weight of electric cars can affect the tire noise, because a heavy car usually has wider tires, and the width increases the tire noise.
The loudness of early electric cars may be due to sheer prioritization.
For example, the first Teslas had to be brought to the market in a hurry, so perhaps not so much time and effort was spent on soundproofing the car.
The focus of Tesla’s or any other manufacturer’s market was also not – and still is – on arctic markets like Finland, but on the United States and Central Europe, where the roads are in better condition on average.
When driving on such roads, the tire noise is not as big of a problem, and the manufacturer does not have to put as much effort into it.
Today, however, there are many electric cars in which tire noise is just as effectively dampened as in their combustion engine counterparts. The cars have thick glasses and separately damped subframes and other solutions that dampen tire noise.
Finland’s roads and demanding conditions are not the first thing on the mind of car factories. Here’s HS’s tire test Tesla thanks in Ivalo.
Secondly tires tailored specifically for electric cars may have one aspect that affects tire noise.
In electric cars, range is an important thing, and the range is affected by the tire’s rolling resistance.
That and tire noise are opposites in a way: the lower the rolling resistance, the less energy the tire absorbs and, on the other hand, it dampens less tire noise.
I’m sliding according to tire noise, tire durability and, for example, rolling resistance are important issues that are considered in tire design.
In his opinion, the most important thing is always safety, controllability of the tire in a dodging situation and grip on different driving surfaces.
“That’s always the number one thing. Of course, it would be possible to design a very quiet winter tire, for example, with no transverse grooves in the pattern. But such a thing would be completely useless on snow, so it’s not a relevant idea in any way.”
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