Why noise is one of the biggest problems with electric cars

Imagine your company is engineering the next line of electric vehicles. You create technical specifications that reduce range anxiety, you’ve perfected the colors that pop and entice customers to buy and with battery technology advancement, you’ve priced it right.

But there are problems with electric cars.

Because the electric vehicle engine emits no noise, pedestrians are more likely to be struck by an electric vehicle. A study by the National Highway Traffic Safety Administration indicated that hybrid and electric vehicles are 57 percent more likely to cause accidents with cyclists, and 37 percent more likely to cause an accident with pedestrians, than a standard internal combustion engine vehicle.

Countries are requiring the quietest cars emit a sound to warn those around the vehicle of its presence.

Now, imagine after creating the ideal electric vehicle, the customers reject it based on the noise it emits. What if your vehicle’s noise is too strange or annoying?

This is just one of the many perils facing the quiet electric vehicle.

Why is there a quiet issue?

The goal of successfully getting an electric vehicle to market, one that a consumer would be interested in and enjoying, was about improving range. In a world lacking in electric vehicle infrastructure, solving range anxiety would allow customers to feel more comfortable driving the electric vehicles to-and-from work and longer trips beyond.

Engineers focused on vehicle architecture including the number of motors driving the wheels, managing the HVAC system’s energy consumption and finding ways to reduce weight, such as using thinner panels and less sound deadening components to provide better mileage. Without the roar of a combustion engine, there was no need to reduce noise.

Noise issues in the after-market use was simply a problem no one had anticipated and the realization that noise was a critical aspect in vehicle comfort and safety has come late in the process. The unintended consequence of having a quieter car is the noises, or lack thereof, concerning both passengers and pedestrians.

Quiet Image 1.jpeg

Exterior noise

Without a sound or signal of an electric vehicle’s presence, the likelier it is to be involved in an accident with a pedestrian or cyclist.

“The greatest risks associated with electric vehicles are when they are travelling at low speeds, such as in urban areas with lower limits, as the noise from tires and the road surface, and aerodynamic noise, are minimal at those speeds,” said Kevin Clinton, road safety adviser at the Royal Society for the Prevention of Accidents.

The pedestrians most at risk are the blind, where studies have suggested that 93 percent indicated problems with electric vehicles.

“Guide dogs are all about giving people confidence and independence, and a near miss or an incident with a vehicle of this type could really set people back a long way,” said James White, campaign manager at the Guide Dogs for the Blind Association.

Along with the quiet on the streets, electric vehicles pose a significant risk in parking lots or near driveways where pedestrians may be jogging, shuffling kids to-and-from a store or walking a dog. With no engine noise, there’s no warning other than the reverse lights on the car.

Governments are now creating rules that require electric vehicles to emit noises for public safety. Starting in July 2019, the European Union will require all new electric and hybrid vehicles sold in Europe to emit noise. As of 2021, older vehicles will need to be retrofitted with a sound to warn pedestrians.

However, there is no one specific sound a car needs to make so the concept of city streets sounding like a Las Vegas casino isn’t far-fetched. Imagine every car wailing like a truck backing up. And when was the last time you paid attention to a car alarm? Sensory overload due to countless warning signals is likely to desensitize awareness and the efficiency of the signals.

As the electric vehicle consumer market is about to ramp up, the possibility of multiple chirps, buzzes and tones are going to be heard on the roadways, at least when the vehicle is traveling under 20 miles-per-hour (an approximate estimate where the artificial noise would cease and the natural noises of the tires and the road noise would be sufficient). Can we truly expect the visually-impaired to keep track of every different noise an electric video emits?

The likely noise will sound along the lines of a “futuristic” whir or melodious humming. Examples include Nissan’s singing ‘Canto’ at the Tokyo Auto Show and Jaguar’s space-like drone.

At a recent shareholder meeting, Elon Musk offered his thoughts on these sounds.

“I think the sensible, ideal thing long-term is to have proximity sensors that direct a pleasant-sounding noise in the direction of where somebody is walking — so therefore, it’s the least amount of noise, and it’s not annoying, and it’s only going to where it needs to go,” he said.

Sensor technology, with the continued innovation of autonomous vehicles, will be a likely long-term solution – but short-term electric vehicle interest must be managed. On top of that, determining the difference between a pleasant sound and an unpleasant sound is subjective at best.

Then again, some like the roar of an engine, others prefer a subtler acceleration sound.

Countering Musk’s point is Dan Edmunds, director of vehicle testing at Edmunds, who thought directional sensor technology would be “more trouble than it’s worth” due to the developmental issues facing autonomous vehicle manufacturers.

“That sounds more expensive, frankly,” he said. “It seems like that just adds unnecessary complexity.”

For the time being, since the ‘autonomous’ option isn’t there yet, the noise generated will be omnidirectional and will probably need to mimic a combustion engine or at least be comparable since that is what people are used to hearing in the cities.

Until, or unless, rules and regulations dictate the specific sounds that must emit from electric vehicles, automakers will have to engineer sound development that effectively communicates the presence of an electric vehicle without becoming too cumbersome or easily ignored.


Hybrid and electric cars continue to grow in popularity, and major progress is being made as engineers address the sound concerns by adding active noise inside and outside the vehicle.

For the interior, using a broader brand spectrum creates a great level of comfort on the ears and the annoying sounds once hidden by a combustion engine can be drowned out via the speaker system, without adding much cost. Creating it for lower power consumption won’t hinder the batteries’ performance, either.

Governments are also taking action to ensure the safety of pedestrians. Along with the European Union’s rules, Japan, for example, has regulations currently in place to address the exterior noise problems, and soon this will include the character of the noise.

Slowly, the noise problems with electric vehicle will be minimized. Going forward, and this includes autonomous vehicles, engineers will need to remain vigilant on the unintended consequences from managing one problem and how solving one issue may impact public safety.

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This article first appeared on the Siemens Digital Industries Software blog at https://blogs.sw.siemens.com/thought-leadership/2019/08/07/why-noise-is-one-of-the-biggest-problems-with-electric-cars/