First publishedin ITS International
Harman's HALOsonic technology offers significant improvements in safety for hybrids in urban environments
The growing popularity of hybrids and electric vehicles gives rise to new safety issues in urban environments, as many of the aural cues associated with engine noise can be missing. The solution is to intelligently make vehicles noisier
The rise in popularity of hybrids and Electric Vehicles (EVs) is a result of environmental pressures, shifts in taxation and emerging technologies for batteries and motors. Competition among the car manufacturers means these vehicles need to be cost effective to buy and operate, plus fun and rewarding to drive. These requirements are often in direct conflict with each other and can be further compromised by consumer desires for acceptable levels of noise and comfort.
The result is an affordable and increasingly popular vehicle offering nearsilent running which is ideally suited for use in town and city. However, there is a growing concern that these vehicles are difficult to hear, thus increasing the risk of accidents.
A growing risk
According to the US National Highway Traffic Safety Administration
(NHTSA) 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 is profound when objectively assessed; testing has shown that at 50km/h an EV cannot be heard until it is just 3m away. That compares to a distance of around 10m away for a conventional-engined car. The additional time gained, hearing the car from further away, could otherwise allow the pedestrian a chance to reach a place of safety in time.
With compelling evidence, legislation was inevitable. In January this year, President Obama signed the Pedestrian Safety Act (S. 841). Introduced by Senator John Kerry, the new US law directs NHTSA to determine "performance requirements for an alert sound that allows blind and other pedestrians to reasonably detect a nearby electric or hybrid vehicle operating at low speeds". Crucially, the law will require that the vehicle generate the sound automatically and driver-initiated sounds found on the Nissan
Leaf or Chevrolet Volt won't satisfy the legislation.
The US may have been first but Europe and Japan, the country with the most hybrids, are working on their own legislation. The Japanese in fact released guidelines for external sound for quiet vehicles in 2010, stipulating an 'enginelike' sound.
With the numbers of hybrids and EVs set to grow and an ambitious target set by President Obama to have one million plug-in vehicles on the road by 2015, a scalable and cost-effective solution is required by car makers. The most advanced solution is currently provided by leading acoustics and vehicle electronics specialists Harman in partnership with Lotus Engineering. Dubbed HALOsonic
, it offers a range of solutions delivering both internal (that is, inside the vehicle cabin) and external sound synthesis. The core of the easy-to-implement and lightweight technology is a software algorithm originally created to rapidly process active suspension systems on F1 cars.
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 through the car's conventional audio system.
"The system is about generating a sound, not noise pollution," says Harman's director of active noise control, Jon Lane. "The speaker is placed at the front of the car so it can be heard from farther away but also so the sound decays much more quickly than that from an internal combustion engine. We therefore offer the best of both worlds for sound." Sound maps undertaken by Lotus present an interesting view of where sound is generated in a car and the ability through technology to fine tune this. Ensuring sound is further reduced to minimal levels, the system can be turned off at around 50km/h because tyre and road noise take over as the primary sound source(s).
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 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 city dwellers could be subjected to a confusing and distracting array of sounds that could be very unpleasant and ones that the brain doesn't compute as traffic."
Sound synthesis ensures pedestrians hear the vehicle from further away giving time to react