Electric Vehicles – A Sound Idea

How can manufacturers ensure that the growing number of electric and hybrid cars remain engaging and joy to drive yet satisfy consumer and environmental desires for lower levels of noise? Could a controlled sound generator be the convincing solution?

The growing popularity of hybrid and electric vehicles is a result of environmental pressures, shifts in taxation and investment in new technologies for batteries and motors. The car manufacturers are responding and many now offer a hybrid or electric vehicle in their line ups. The growing competition means OEMs must both differentiate, offer a rewarding drive yet retain the features that have become standard in conventional vehicles. Refinement is one example and the near silent running of an EV, ideally suited for use in town and city is a feature that early adopters of the cars like. However, there is a growing concern both among safety groups, governments and groups that rely on sound that these vehicles are difficult to hear and the risk of an accident with one is greater.
A Recognised Risk
According to NHTSA (National Highway Traffic Safety Administration) in the USA, in scenarios such as those ‘in which a vehicle is slowing or stopping, backing up, or entering or leaving a parking space, a statistically significant effect was found due to engine type. The Hybrid or Electric Vehicle was two times more likely to be involved in a pedestrian crash in these situations than was an internal combustion vehicle.’
The lack of sound from hybrid and electric cars when compared to combustion engine cars is remarkable when assessed in a like for like scenario Tests undertaken show that at 50km/h an EV cannot be heard until it is just three metres away. Compare that to 10 metres away that is the distance for a conventional engined car and the risk in an urban environment is apparent. The time gained just from hearing the car from further away, could enable a pedestrian to respond or get out of the way.
With compelling evidence and a growing number of people affected by the cars as their numbers also rise, legislation was inevitable, commencing with the US President signing the Pedestrian Safety Act (S. 841). Crucially, the law will require that the vehicle generate the sound automatically. Systems whereby sounds initiated by the driver, such as those found on the Nissan Leaf could struggle to meet the proposals.
The US may be addressing the problem but the UK, Europe and Japan, the latter a country with the most hybrids on its roads, are working on their own legislation with the Japanese releasing guidelines for external sound for quiet vehicles in 2010, stipulating an ‘engine-like’ sound.
Developing a cost effective solution for the world’s electric cars
With the number of hybrids only set to grow further and a growing number of makers offering electric and hybrid cars in the UK marker, a scalable and cost-effective solution that meets any legislation planned is needed by the car makers. The most advanced solution, already available, is provided by leading acoustics and vehicle electronics specialists HARMAN in partnership with Norfolk-based Lotus Engineering. HALOsonic, in reference to the partnership (HARMAN and LOtus)is a range of technologies developed by the firms to deliver both internal (in the car) and external sound synthesis.
Carefully considering the nature of the vehicles and a requirement to possibly fit the technology to existing car platforms, the HALOsonic products are easy to implement and extremely lightweight. The core of the technology is a software algorithm originally created to rapidly process active suspension systems on F1 cars. Now, in an unusual technology transfer, racing cars are helping make road cars a little more noticeable in our urban environments.
Using inputs from throttle position and vehicle speed, a central processor generates an authentic engine-like sound that is played back through a speaker in the front bumper and equally through the car’s conventional audio system. ‘Our system is about generating a sound, not making unwanted noise,’ says HARMAN’s Director of Active Noise Control, Jon Lane. ‘The ruggedised external speaker is placed at the front of the car so it can be heard from further away but also so that the sound decays much quicker when the vehicle has passed. You don’t get that with an internal combustion engine. With HALOsonic we can offer the best of both worlds for sound.’
Mapping of the sources of sound from a car present an interesting view of where sound is generated and the ability through technology to fine tune this. Stressing the point further that this technology is not about making noise, the system can be turned off at around 50km/h. ‘At this speed, tyre and road noise take over as the primary sound source,’ suggests Lane.
The sound processor mimics the petrol engine’s pitch and frequency, so pedestrians can identify the vehicle’s speed, direction and distance ‘We have worked hard with organisations representing those affected to ensure that the characteristics are as authentic as possible,’ adds Lane. ‘A synthesised engine noise is currently the most recognisable sound for a vehicle to make, as recommended in the recent Japanese guidelines. If the sound is not ‘engine-like’ pedestrians and other groups affected such as guide dogs could be subjected to a confusing and distracting array of sounds that could be very unpleasant and ones that our senses doesn’t compute as traffic. ‘From a pedestrian recognition point of view, the mix of high frequency and low frequency sounds that a normal engine makes is quite important,’ suggests Colin Peachey, Group Chief Engineer at Lotus Engineering. ‘Low frequency sound – 50-100 hertz travels farther, so you get an early warning. But high frequency sound is associated with where the sound is coming from it’s more directional.’
For groups who rely on sound such as the partially sighted and their guide dogs, this is a crucial aspect and backed up by The Royal London Society for the Blind. ‘If a blind person wishes to cross a road, they will use sound as their main navigation aid,’ says Dr Tom Pey, Chief Executive of the Royal London Society for the Blind. “The most common form of road accident involving blind people is collisions with bicycles – because the bicycle is the most difficult thing to hear. Without a simple modification to electric cars, we face even more dangers.”
Adding Intelligence
To develop the system that will create the appropriate sound, HARMAN has carefully analysed the duty cycle of the electric powertrain. ‘We have implemented an engine ‘idle’ sound when the vehicle is switched on and when the handbrake is released as this is when the vehicle is ready to move,’ says Lane. ‘A reversing sound can also be specified.’
Adding More
In partnership with Lotus Engineering, HARMAN has been actively presenting the technology to everyone from school children in Oxfordshire to vehicle manufacturers around the world to refine the system requirements for each market and territory. Whilst legislation is likely to mandate a minimum sound level, some car manufacturers are considering introducing the technology regardless of legislation as a means of differentiation. ‘Whilst safety is the key driver for the change, manufacturers are also seeing it as an opportunity to use the sound to convey brand characteristics,’ says David Howlett from Oxfordshire-based MMR Research, an organisation that conducted significant consumer research in this area. ‘By having sophisticated sound synthesis capability within the car, it becomes possible to develop sound-based sensory signatures which can be active within or even outside the car.’ Others suggest that the internal sounds could become as fashionable as ringtones with the ability to download new ones on regular basis.
For vehicles large and small
Whilst most of the development has been done using passenger cars, the sound synthesis technology is relevant to the growing number of electrical light commercial vehicles used for pick up and delivery operations in urban environments. Growing in popularity in the UK and across the Continent, and often used at unsociable hours of the day, operators have increasingly preferred electric vehicles for the quieter running and the ‘green’ marketing benefits. Operators range from energy suppliers, supermarkets and larger distribution firms keen to be an early adopter. ‘We have spoken to operators about installing sound synthesis systems, for the EV fleets,’ adds Lane. ‘These vehicles will be equally affected by the legislation so those first to use the technology could present themselves as forward thinking, safety conscious and ahead of the game.’ A rise in the number of hybrid buses, a number of which are being trialled by London Transport is also a potential market. With pedestrians inevitably in close proximity of these buses, it’s an obvious application for the technology,’ suggests Lane.
A technology that is ready today
As a pioneer of the technology and one for the first to have it ready for mass production at an affordable level, it is perhaps unsurprising that HARMAN will have a European OEM adopting the technology for one of its road cars in 2013. ‘We’ve been able to develop and supply robust components that will meet the rigorous standards set by the OEMs,’ concludes Lane. ‘Demonstration cars are available in the UK for those interested in how the technology works in the real world. As legislation seems ever more likely in these key markets, it is vital that we gather and input the opinions and desires of everybody likely to be affected. We welcome comment and feedback from those in the transport infrastructure network as to the effects of this technology.’