A sound idea for electric vehicles

9 November 2009

Advanced loudspeaker technology designed to alert pedestrians and road users to the approach of otherwise silent electric vehicles is to be launched on production vehicles for the first time next month.

Jointly developed by engineers at Lotus and audio specialist Harman International, the system — which allows users to choose from a range of engine sounds — has already been demonstrated on a Toyota Prius and will be launched on a low production run of unspecified electric fleet vehicles next month.

Lotus engineer Andy Mackay explained that the launch of the technology — which matches the sound to the speed and acceleration of the vehicle — coincides with growing concerns that silent or extremely quiet vehicles pose considerable accident risk to unwary pedestrians. The US and Japan are now considering introducing legislation to set minimum levels of noise for quiet cars, while the UK government is set to debate the issue in the coming weeks. Interestingly, Mackay added that there could even be a case for deploying the technology on some of today’s quieter petrol engines.

The technology is the first element in a suite of so-called active noise control technologies developed by the two companies.

As well as internal sound synthesis — which would enable the driver of a silent electric car to pretend they’re at the wheel of a V6-powered SUV — the groups are also planning to launch a road noise cancellation system that would cancel out noise from the tyres and the road. Set to enter production next year, this uses accelerometers to detect noise-inducing vibrations and generates a correction signal that is broadcast through the cars’ speakers to cancel out the noise.

Mackay said that, because accelerometers react to vibrations rather than sound, the system doesn’t interfere with the car’s stereo system.

Jon Excell