Making EVs 'noisier' for safety

From next year onwards, electric cars should begin to increase in numbers as Nissan starts marketing the Leaf, the world’s first mass-produced electric vehicle (EV). While some other carmakers have offered EVs in past years, these have been in limited numbers and in specific localities. Nissan aims to offer the Leaf in as many countries as possible and make EV usage increase like hybrids have over the past 10 years.

Since the zero-emission concept version of the Leaf was unveiled last August, Nissan has been continually refining the model. Among the enhancements to the test units is the "Approaching Vehicle Sound for Pedestrians" system, which will also be installed in the Nissan Fuga hybrid that will go on sale in Japan during the fourth quarter of this year. The sound system is the first of its type to be introduced by an automaker.

The development of this system is in response to public concerns about the exceptional quietness of EVs which create safety issues for pedestrians, especially older people who may have their hearing ability diminished. Visually-impaired people would also find it hard to detect an approaching EV and could accidentally step into its path.

As a socially responsible company, Nissan wants to ensure its products do not endanger anyone so it is making the “Approaching Vehicle Sound for Pedestrians" system (perhaps some catchy name or acronym will be used when the model is launched) standard in the Leaf. The system is said to make it easy for those outside to hear the vehicle approaching, but the sounds will not distract the driver and passengers inside. Thus, pedestrian safety as well as driver and passenger comfort are met.

In developing the sound system, Nissan carried out behavioral research of the visually-impaired and worked with cognitive and acoustic psychologists. After looking at applied original technology developed to reduce vehicle noise and conducting tests in Japan and abroad, the system was created.

The sine-wave sound system sweeps from 2.5kHz at the high end to a low of 600Hz, an easily audible range across age groups. The researchers avoid having a sound range that would add unnecessary noise to the environment (around 1,000Hz).

Depending on the speed and status (accelerating or decelerating) of the Leaf, the sound system will make sweeping, high-low sounds. For instance, when it is started, the sound will be louder, so a visually-impaired person would be aware that a nearby car is about to move. With an EV, there is no engine to fire up so it is like a light switch – just the press of a button and the vehicle is ready to move. And when the Leaf is in a reversing motion, the system will generate an intermittent sound. The sound system ceases operation above speeds of 30 km/h as regular road noise is then high. It will come on again when the Leaf’s speed falls below 25 km/h.

The idea is clever and would certainly contribute to road safety but what happens when the number of Leafs becomes so plentiful that there may be 5 or 6 in close proximity crawling around a crowded basement carpark as drivers search for a space? The slow speed would mean the system will be in operation and many Leafs beeping simultaneously - even if the sound is low - could become irritating. For some, even the sound of a reverse sensor beeping can be irritating so imagine what it would be like in congested traffic!

The system is controlled through a computer and synthesizer in the dash panel, and the sound is delivered through a speaker in the engine compartment. A switch inside the vehicle can turn off sounds temporarily but the system automatically resets to "ON" everytime the ‘ignition’ is turned on.

The Leaf will go on sale in Japan, North America, Portugal and the Netherlands in December 2010 and in the UK and Ireland from February 2011. More extensive marketing will start in 2012. According to Edaran Tan Chong Motor, Nissan is keen to offer the Leaf in Malaysia in future but whether it will be practical to do so depends on issues like the recharging infrastructure and of course, whether there are meaningful incentives provided by the government for zero-emission vehicles so they are reasonably priced. The model will be manufactured at Nissan factories in Japan, UK and USA.

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