Exclusive: Selecting a 'voice' for the Renault ZOE wasn't easy
Creating a car that runs on nothing more than bog standard electricity was the easy part of Renault's latest foray into zero emissions motoring... Giving it a voice was not so trouble-free.
Save the planet it might, but the major issue with a vehicle that is propelled by electric motors is the fact they don't produce a sound when driven at low speeds - particularly troublesome around the streets of busy towns and cities.
"There is no EU law as yet that says an electric vehicle must produce a sound," says Renault's Deputy Chief Vehicle Engineer on ZOE David Twohig. "But we wanted to cover all bases with ZOE and create something that wasn't just safe for the driver but also pedestrians," he added.
It wasn't as easy as simply recording the sound of a combustion engine and playing it through a speaker as Twohig explains: "the idea was to create an identity for ZOE but one that was audible yet not noisy. ZOE had to care for the environment in more ways than one and noise pollution is a big problem in major cities."
Renault boffins then called upon specialist sound engineers at Sound Perception and Design Team at the research institute IRCAM (Institut de Recherche et Coordination Acoustique/Musique) to create a bespoke noise - or 'voice' as the French firm calls it - that would emit a frequency that humans can hear yet doesn't penetrate the cabin and irritate the occupants. From inside, the noise is barely audible.
"We then had to test this new sound on the vulnerable, so that involved inviting volunteers from the European Blind Union to our research centre to allow us to fettle the sound for optimum safety levels," explains Twohig.
But just when Renault engineers thought they had cracked the perfect noise, they broke for lunch and everything fell apart.
"We were walking to lunch when one of the guide dogs leading our volunteers stepped out in front of a passing ZOE.
"Luckily the driver managed to stamp on the brakes in time but we quickly realised the dogs couldn't judge an oncoming vehicle's distance from the sound we had manufactured."
The sound experts soon worked out that guide dogs have been trained from a very young age to listen out for the sound of cylinders combusting and it is this noise they use as a yardstick to judge the distance and speed of an oncoming vehicle.
"Our engineers had to go back to the drawing board and the three 'voices' that the ZOE now produces feature a low frequency bass track that mimics the sound of a combustion engine," says Twohig.