[Quietcars] FW: [nfbwatlk] FW: [Caps] Fw: Economist article on our hybrid research

Tue May 12 01:23:38 UTC 2009

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From: nfbwatlk-bounces at nfbnet.org [mailto:nfbwatlk-bounces at nfbnet.org] On
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Sent: May 11, 2009 11:26 AM
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Subject: [nfbwatlk] FW: [Caps] Fw: Economist article on our hybrid research

Economist article on our hybrid research

Link also included.

  The sound of silence
  Economist - UK

Economist

Electric cars and noise

The sound of silence
May 7th 2009
>From The Economist print edition

Sound generators will make electric and hybrid cars safer

WHEN cars run on electric power they not only save fuel and cut emissions
but also run more quietly. Ordinarily, people might welcome quieter cars on
the roads. However, as the use of hybrid and electric vehicles grows, a new
concern is growing too: pedestrians and cyclists find it hard to hear them
coming, especially when the cars are moving slowly through a busy town or
manoeuvring in a car park. Some drivers say that when their cars are in
electric mode people are more likely to step out in front of them. The
solution, many now believe, is to fit electric and hybrid cars with external
sound systems.

A bill going through the American Congress wants to establish a minimum
level of sound for vehicles that are not using an internal-combustion
engine, so that blind people and other pedestrians can hear them coming. The
bill's proponents also want that audible alert to be one that will help
people judge the direction and speed of the vehicle. A similar idea is being
explored by the European Commission.

Although there is little data on accidents, the latest research suggests
there is cause for concern. Vehicles operating in electric mode can be
particularly hard to hear below 20mph (32kph), according to experiments by
Lawrence Rosenblum and his colleagues at the University of California,
Riverside. Above that speed the sound of the tyres and of air flowing over
the vehicle start to make it more audible.

The researchers made sophisticated recordings of Toyota Prius hybrids
running on electric power and petrol-engined cars approaching at 5mph from
different directions. These were played to a group of subjects wearing
headphones. The subjects were asked to press one of two buttons to identify
which way the vehicle was coming from as quickly and accurately as possible.
As expected, they could determine the direction of the petrol-engined cars
much faster. When natural background sounds, like the engine tickover of a
parked car, were added, the hybrids' direction sometimes could not be
detected until they were perilously close. Both sighted and blind subjects
gave similar results.

Beep, beep

Dr Rosenblum and his colleagues recently repeated the experiment outside in
a car park. This time blindfolded subjects stood three metres away from the
point where the vehicles passed. The researchers found that the hybrid
vehicles had to be around 65% closer to someone than a car with a petrol
engine before the person could judge the direction correctly.

What sort of noise should electric-powered cars make? They could, perhaps,
beep as some pedestrian crossings do, or buzz like a power tool. Having
worked with blind subjects, Dr Rosenblum is convinced of a different answer:
"People want cars to sound like cars." The sound need not be very loud; just
slightly enhancing the noise of an oncoming electric vehicle would be enough
to engage the auditory mechanisms that the brain uses to locate approaching
sounds, he adds.

Systems to do this are already being developed. Lotus Engineering, the
consultancy of a British sportscar-maker, recently signed an agreement with
Harman Becker, a producer of audio systems, to commercialise one. Lotus has
worked on a number of hybrid and electric vehicles and it was while these
were moving around its factory that the engineers thought they would be
safer if they made a noise.

The system Lotus uses was originally developed for a different reason: to
cancel out intrusive noises inside a car. Sound-cancelling works by
analysing any unwanted frequencies and then producing counteracting ones.
The Lotus system was adapted so that it could also produce sounds that
change with speed and use of the throttle, providing a familiar audible
"feedback" to drivers of vehicles with a silent engine. Adding external
speakers allows pedestrians to hear the noise too.

It is possible to create a different sound within a car from the one that is
heard outside, says Colin Peachey, a chief engineer with Lotus.
Manufacturers could create their own sounds according to how they perceive
their models. Carmakers already take engine noises seriously enough to use
acoustic engineers to tune exhaust pipes, especially for high-performance
cars. Drivers of electric cars might in future even be able to select
different engine sounds, and maybe download them like ringtones.

Although some drivers might want to cruise in an electric car thundering to
the sound of a mighty V8 engine, it is not necessary-and traffic police may
have something to say about it. Synthesised engine noises could even help
reduce noise pollution, says Mr Peachey. For instance, sound from the
speakers at the front of an electric car (or the rear if
reversing) is highly directional. This means it is more likely to be noticed
by pedestrians in front or behind the vehicle. The noise from an internal
combustion engine, however, radiates in many directions-including upwards
into offices and bedrooms.

Unique engine noises would still be possible. A sound-generator will be
fitted to the Fisker Karma, a luxury plug-in electric hybrid which goes into
production later this year. It will both alert pedestrians and enhance the
"driver experience", says Russell Datz of Fisker, based in California. As
the Karma uses new technology it is fitting that its sound should also be
new, he adds. But Fisker still has to decide what a luxury electric car
should sound like.

--
Lawrence D. Rosenblum
Professor
Department of Psychology
University of California
900 University Ave.
Riverside, CA 92521
USA
Office: 951-827-4400
Cell: 310-903-3079
FAX: 951-827-3985
rosenblu at citrus.ucr.edu
http://www.faculty.ucr.edu/%7Erosenblu/
Laboratory demonstration page:
http://www.faculty.ucr.edu/~rosenblu/lab-index.html
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