In their basic form, electric cars are silent. Hans Zimmer wants to change that.
The Oscar-winning composer behind Gladiator and The Dark Knight is turning from the silver screen to the open road to answer a question that the industry has been considering for years: what should an electric car sound like?
For a century, the unmistakable drone of pounding pistons has resounded from vehicles, from the smallest hatchback to the loudest racing car. A world running on battery power wipes the soundscape clean.
“This is a chance to end the dictatorship of the internal combustion engine,” said Zimmer.
“We have an opportunity to go back sonically to a pre-industrial revolution type of environment [before the combustion engine]and then to something completely new.”
He is working with BMW to develop a series of audio cues, from the noises when a car starts to the rising pitch when it accelerates, to use in its electric models.
This year, sounds created by Zimmer and a team from BMW will feature in two new models, the electric iX and i4 cars.
Dedicated audio teams working in carmakers from Detroit to Japan are tackling the same question. Perhaps not surprisingly, the answer to how an electric car should sound varies wildly.
Porsche, a brand intrinsically linked to purring engine tones, has tried piping artificial noises into the cabin of its Taycan, Jaguar has used a digitally growing noise in its electric I-Pace, while early Nissan Leaf cars made an “alien-like” whistling sound.
But for its new range of battery models, Nissan polled drivers and found that most simply wanted silence.
“They really enjoy the silent driving feedback experience,” said Paul Speed-Andrews, who leads the company’s audio team in Europe. “People universally want the thing to be quiet.”
Paul Speed-Andrews, who has worked at Nissan’s European technical center for 16 years, is an expert in noise and vibration
Renzo Vitale, BMW’s creative director of sound, said the right noise can help make electric vehicles safer
“It’s fair to say the majority of our customers consider our vehicles as a functional object, it’s not a sports car,” he added.
BMW, on the other hand, says it wants to use sound to make drivers feel more connected to their electric vehicle and enhance the motoring experience.
The acceleration noise created by Zimmer draws on the Shepard Tone, an auditory illusion of a constantly rising tone that he used to build tension in his score for the film Dunkirk. With the car set to the sporty “dynamic” mode, it also includes a note that starts in a low register and continues to drop as the pace picks up.
But the risk is that racing pulses lead to faster driving.
“The emotion of driving should be fabulous, but we would also like to achieve a safer driving experience,” said Zimmer. The right sound can help make vehicles safer, he added.
“If you think about it, it’s so obvious to me that we think of the eyes looking ahead in the road as the main way of maintaining safety, but really it’s our ears that have full surround where we pick up info about how safe we are .
“Sound determines our emotion, so we can use that to help to make [the cars safer].”
When creating the sounds of an electric car, composers are torn between replicating engine sounds and experimenting with new options.
The team at Volkswagen tried out orchestral and electronic sounds, and opted for the latter, said Indra-Lena Koegler, one of the audio engineers on the project. Even so, they were conscious of not putting potential customers off with irritating noises.
“If someone is in love with the shape and you come along with a strange sound, the customer might say that’s not me, I’m leaving,” said Klaus Bischoff, head of design at VW.
Nissan decided in the end that the sound of its electric cars needed to be “somewhere near a petrol engine”.
“Anything we generate has to be seen as an authentic sound that is associated to a vehicle, it can’t be birds chirping,” said Speed-Andrews.
BMW has opted for a blend of traditional instruments and synthesized sounds, with female choral voices used when the vehicle turns on and acoustic horns and strings for the more relaxed “expressive” driving mode.
“When we mentioned this in BMW development meetings, no one believed this approach could make sense,” said Renzo Vitale, creative director of sound at BMW who worked with Zimmer on the audio project.
“But the first time the board [members] sat in the car and drove, they came back and said ‘I felt like a composer driving the car’.”
The external sound of the vehicle is also very important to comply with pedestrian safety regulations.
One option Nissan has used consists of two tones, one more high pitched at 2,500 hertz to cut through other sounds, the other at a lower frequency of 800 hertz that tends to be easier for older people to hear.
“This avoids anything around 1,000 hertz, which is where most of the noise is,” said Speed-Andrews.
The Japanese carmaker also experimented with a system that would direct sound at people in front of the car.
It used sensors in the car to identify people and an array of six speakers at the front allowed it to blast a warning directly at anyone about to cross the road while leaving other passers-by in silence.
The project has yet to make it on to a vehicle in production, but is an option for when sensors for autonomous driving become commonplace on its vehicles, said Speed-Andrews.
As rival carmakers pursue different sonic paths, Zimmer believes it makes sense to discuss a co-ordinated plan to avoid an urban cacophony of jarring pitches and noises.
“One of the things I’m going to try to bring up in the future is with all the other sound designers from all the other companies,” said Zimmer. “Is there a way we can find a harmonious way of doing it?”
Cameras, which are becoming a common feature on vehicles, could allow sounds to be changed depending on the external environment.
Zimmer said the first question he asked after signing up with BMW was whether it would be an option to change the soundscape depending on the setting of the journey, whether that was the exhilarating views of a mountain pass or the quieter experience of travel at night.
“When I write for film, I write for the protagonist,” he said, “but when I write for a car, I am the protagonist”.