Analysis: How EVs are sparking a noise revolution

BMW Group sound designer Renzo Vitale said: “We’re defining a new paradigm. There’s a shift in how the energy [for car propulsion] is created. With an internal combustion engine, there’s a pitch change when you’re accelerating, and it’s an intensifying sound. With an internal combustion car, people are used to that sound, and they’re expecting it. In an EV they’re expecting the same, but that makes no sense.”

Instead, Vitale says BMW wanted a sound that showcases how EVs offer “a new world that didn’t exist.” “It’s about communicating an emotion,” he explained.

Of course, people have perceptions of what electric cars should sound like, which prompted some companies to trial systems that met those expectations. For example, when developing the Jaguar I-Pace, Jaguar tested a noise inspired by a science-fiction spacecraft. However, it abandoned that idea when pedestrians looked up at the skies rather than at the road when they heard it.

Fredrik Hagman, Volvo’s interactive sound designer, said the Swedish firm quickly ruled out any “novelty” sound concepts, commenting: “This is a sound that’s always on, and we’re going to be stuck with it for 30 years.”

Another challenge he mentioned is that “we don’t want to create noise that will be disruptive; we need to keep the advantages of electric cars”.

Hagman continued: “We realised that just because there’s no combustion engine, it doesn’t mean an electric car is silent. It still makes lots of noises, such as the noise of tyres on the road. So our approach was to keep it natural and enhance those sounds, rather than add a new sound.”

Volvo’s research found that such a sound is recognisable to other road users, easy for them to locate and “non-intrusive and non-polluting”, according to Hagman. It also has the benefit of becoming hard to notice when the car reaches 20kmh and the noise stops.

Volvo’s artificial noise is essentially a low hum; the very basic sound was taken from a recording of ocean waves. While clearly heard in an echo-masking anechoic chamber, it’s virtually indistinguishable from road noise if a car goes past under electric power.

“We wanted to raise awareness without making people look,” said Hagman. “We didn’t want a head-turner.”

BMW is taking a slightly different approach. Vitale has been working with Hollywood composer Hans Zimmer to develop a sound for its EVs. “We want to go for something unexpected,” said Zimmer. “Technical is not our approach now; we want new possibilities. We use relationships that can be related to chords, but it’s not musical.”

The duo produced a trial noise for BMW that Vitale described as “very musical, and triggered by the driver, who is a performer”. “The driver expresses himself,” he said.

The Italian also composed the sound for the forthcoming Mini Electric, taking a slightly different, “human” approach. He described it as “friendly, with a hint of go-kart”.

Another challenge with AVAS is to determine where the noise actually comes from. Jaguar put a speaker behind the I-Pace’s front grille, for example, while Volvo uses an underbody speaker that bounces the noise off the road.

AVAS are also required when cars are reversing, because it’s particularly important to warn people when the car is moving in an unexpected direction.

Hagman said Volvo was initially keen to avoid a beeping noise similar to those used by commercial and construction vehicles but that “after some trials, we found this was a very logical sound”. This prompted Volvo to use a “synthetic” beeping that was softened to “make it sound less trucky.”