Audi's acoustic engineers are deciding the best way to break the silence of the brand's forthcoming 'e-tron' electric cars. At speeds of up to 15mph, they make virtually no sound but Audi is considering ways to introduce noise in order to alert other road users to their presence.
Drawing inspiration from numerous sources, including science fiction blockbusters such as 'I, ROBOT' (which featured the Audi RSQ electric coupe), engineers hope to create an 'engine note' that reflects the nature of these cars.
The risk to other road users and pedestrians of cars driving in near silence is obvious. There is only one logical conclusion for the sound technicians at Audi: The electric car of the future needs its own sound - but which one?
"We speak of quiet cars when an electric car is driven at up to 15mph," explained Dr Ralf Kunkel, Head of Acoustics at Audi. Noise from the tires and the slipstream is evident above this speed, at which point an electric car is no longer significantly quieter than a conventional vehicle.
However, the lack of noise is another factor in the attraction of electric vehicles, since environmentally friendly cars should not only reduce emissions, but also noise pollution. The problem arises because drivers use their sense of hearing in traffic to monitor 360 degrees of their surroundings, while the eyes can only cover a limited angle. Therefore, people who are distracted or with poor vision can easily overlook a car that makes no noise.
Organizations for people with impaired sight are advocating for quiet cars to have a unique sound; specifications or laws to this effect are already in place in the USA and Japan.
So the sound technicians at Audi have taken on the task of protecting pedestrians in the electric mobility era. "One way do this is by generating artificial noise in electric cars," said Kunkel.
The acousticians are working on the sound characteristics of the Audi e-tron. It is not just a matter of safety, but also a question of how the Audi of the future should sound. "The obvious approach would be to work on the basis of the familiar sound of a combustion engine," said Christian Schuller, Head of Brand Development/Corporate Identity. "On the other hand, we want to underscore that an electric or hybrid Audi is an innovative product."
Sounds such as the rustling of leaves or twittering of birds are therefore not viable. However: "The sounds used for space ships in films are reminiscent of car sounds, yet are also very different, making this an interesting approach," said Kunkel.
An Audi will not sound like an aeroplane or a space ship from a science fiction film any time soon, though. "But the sound will be new and unusual. The Audi RSQ from 'I, Robot' gives an indication of how an Audi might sound in the future."