Close your eyes and identify that car by its sound. Is it a V6 or V8 or one of the new small three-cylinder gasoline engines propelling minicars?
'The sound of the engine is important. It helps define the image of the car. For some people, it can even make the difference in the purchasing decision.
And that poses problems for the makers of electric vehicles, whose engines don't make any noise at all.
Because they are soundless at low speeds, electric vehicles also pose an obvious danger to pedestrians, bicyclists and others who may not see - or hear - them coming.
At premium carmaker Audi, that has led to the conclusion that electric vehicles will need their own sound. But what kind of sound?
"We talk about Quiet Cars, when an EV travels at speeds up to 25 kilometers and hour," said Ralf Kunkel, who heads the acoustics division at Audi. At these speeds, EVs make hardly any noise at all. When they go faster, wind and tires start to generate more noise.
Studies show that people rely more on their ears than on their eyes to detect traffic. That's why, worldwide, organizations supporting the interests of blind people have called for giving EVs their own sounds. Legislation is already in the works in Japan and the US.
At Audi, sound technicians are working on defining what sound the future e-tron EVs should have. Audi's Kunkel doesn't say what the e-tron will sound like. "Spaceship sounds, such as we see in movies, remind you of cars but are very different, so that's an interesting approach," he says. "In any event, it will be new and unusual."