The near-silent operation of electric cars could bring a welcome reduction in noise on busy roads, but it also poses a risk to pedestrians and other vulnerable road users.
Nissan has developed a 'noise' for its Leaf, which goes on sale in the UK next year, so that pedestrians and cyclists can be alerted to its presence.
The appropriately named Approaching Vehicle Sound for Pedestrians (AVSP) system uses frequencies ranging from 600Hz to 2.5kHz, depending on the speed of the car and whether it is accelerating on decelerating.
Luckily you don't have to imagine what that sounds like because Nissan has released some footage of AVSP in action.
Nissan says the frequency of the noise is enough to alert pedestrians and cyclists to the presence of the car without adding unnecessary noise pollution to the environment. Judge for yourself.
The noise, which is controlled by computer and generated by a speaker in the engine compartment, can be temporarily switched off.
Lotus has also developed fake sounds for its plug-in Evora concept car, although it's mainly for the benefit of the driver. The Evora 414E's Halosonic sound system can generate the sound of a V6 or V12 engine, along with a futuristic noise like a fighter from Star Wars, according to the company.
What noise do you think an electric car should make?
Mobile ringtones and celebrity voices for sat-nav systems have proved popular with consumers, but what noises do you think would suit electric cars such as the Leaf?
If you could have your electric car make any noise, what would it be?