Why electric vehicles don't glide silently through the streets

BERLIN: Electric cars can creep up on you and suddenly come quite close. Now, they make a sort of whirring noise that could just as well be mistaken for a UFO, or a slow sort of plane.

There's a good reason for that fake engine sound, whether it's emitted by a car or an electric bus.

Public transport companies in some places have introduced a uniform artificial sound that could eventually change the audio landscape in our cities.

Those changes will come as local transport gradually goes electric.

Take Berlin, with its 138 electric buses moving through the streets and a further 90 on order.

Nationwide, some 1,500 of Germany's 35,000 buses are electric and the government wants half of the fleet to have alternative drives by 2030.

"The buses are emission-free and therefore climate-friendly on the road," says Werner Overkamp, vice president at a national transport association. "The other big advantage is that they are quiet."

City traffic is anything but quiet, though, and especially in big metropolises, the quiet hum of electric vehicles is lost in the thunderous sound of traffic.

That prompted industry to come up with a special, dedicated artificial sound for electric buses.

In Germany, it's a gentle droning sound that recalls a lift or an extractor fan, swelling or diminishing, higher or lower, depending on the speed. The sound has been dubbed the "friendly neighbour" and all of the nation's public buses are supposed to be making the noise up to about 30kph.

"It is partly a curse that the buses are so quiet," Overkamp says, adding that it's vital for people who are blind or visually impaired to be able to hear vehicles.

Sighted children, the elderly and cyclists also need acoustic signals, according to the German Association for the Blind and Visually Impaired.

If you think about it, and listen closely, there are already lots of artificial sounds out there.

Car manufacturers sometimes hire Hollywood composers and pop producers to give their vehicles a particularly nice buzz or hum.

"Everyone makes their own sound," says designer Fernando Knof. "Maybe you should think a little bit in terms of design concepts."

The winning design for the soothing sound of the bus arose through a student competition, won by Lukas Esser of the Berlin University of the Arts and the sound he called "friendly neighbour."

Life would actually be hard to imagine without artificial noises these days, with the regulation for Acoustic Vehicle Alerting Systems (Avas) introduced EU-wide last summer.

EU-wide, cars must make artificial warning sounds through loudspeakers when driving up to 20 kilometres per hour and when reversing.

Whether the standardised sound for electric buses will be introduced nationwide depends on whether the design wins over public transport companies up and down the country.

They are supposed to specify it in tenders for the purchase of new buses.

However, manufacturers are less keen on a uniform approach, saying that they'd prefer to shape their own sounds, to fit their brand, according to MAN sales manager Uwe Schmid.

Daimler meanwhile says it is focusing on individual solutions from the industry. "We don't consider a one-size-fits-all solution across manufacturers to be expedient."