Why Electric Cars Are Getting Louder
Electric vehicles are notoriously quiet. But new laws are pushing automakers to experiment with unusual noises.
Six years ago, three Volvo engineers sat on a forest floor in western Sweden, picking twigs off the ground and snapping them in half.
“We were in the woods for two days sampling sounds,” recalls Fredrik Hagman, a sound designer at the company. Three hundred sticks later, they returned to the automaker’s headquarters in Gothenburg, Sweden.
There, they tweaked the sound and pitch of the twig’s snap to create the click of the turn signal indicator used on Volvo’s new electric SUV, the XC40 Recharge.
Car companies have always used sound to enhance a car’s personality and boost the perception of its performance. An effective acoustic signature announces the car long before its arrival, and enthusiasts can identify a car’s make and model — and even the year it was built — based on the distant rumble of its engine.
But electric vehicles, which draw power from a battery instead of a noisy combustion engine, don’t make much noise at slow speeds. The quiet can be dangerous for cyclists and pedestrians, who may not hear a car sneaking up behind them, as well as people with visual impairments who rely on sound to detect approaching vehicles.
That’s the reasoning behind a federal law that goes into full effect in September, requiring electric vehicles to make an artificial sound at low speeds and at standstill. The noise must be loud enough to alert pedestrians, and indicate if the vehicle is speeding up or slowing down. For car manufacturers, it’s an opportunity to create distinctive sounds, giving electric vehicles their own flair.
“This is the wild, wild West,” says Jonathan Pierce, senior manager for global experiential research and development at HARMAN International, which designs and engineers branded audio systems for automakers.
Car companies have already begun floating unorthodox ideas. For example, Lincoln hired Detroit Symphony Orchestra musicians to create alerts, blended from percussion and stringed instruments, for its latest SUVs. Meanwhile, BMW tapped Hans Zimmer to compose noises for its Vision M Next, making the concept car sound like the backdrop to an action thriller — like the thrumming, bass-heavy scores for Inception and The Dark Knight.
Road Rules
At speeds above 18.6 mph, both gasoline and electric cars generate noise from wind resistance and tires. But below that threshold, electric vehicles are often silent, which is why the new U.S. regulations require these cars to emit sounds of different frequencies while traveling at speeds up to that limit.
The sounds must vary in volume when the vehicle is accelerating, decelerating and reversing. At standstill, the cars must make a sound of at least 40 decibels, about the volume of a refrigerator softly humming.
Manufacturers usually approach HARMAN with only vague ideas of how they want their electric cars to sound. “We commonly hear, ‘We want our car to sound futuristic,’?” Pierce says. “Often they say, ‘Make it sound like a spaceship.’?”
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