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Making Electric and Hybrid Cars Audible

What Sounds Are Appropriate?

3 min read
Making Electric and Hybrid Cars Audible

There were a couple of news stories this week concerning the efforts of auto manufacturers seeking to add artificial sound to electric and hybrid cars. The reason is that blind persons, pedestrians and others (for instance bicyclers like me) can't hear electric or hybrid cars approaching at low speeds. There is a bill making its way through the US Congress, called H.R.5734 - Pedestrian Safety Enhancement Act of 2008, which ...

"... directs the Secretary of Transportation to study and report to Congress on the minimum level of sound that is necessary to be emitted from a motor vehicle, or some other method, to alert blind and other pedestrians of the presence of operating motor vehicles while traveling."

Once the bill passes, the results/recommendations need to be reported back to Congress within two years.

The US is slow in comparison to Japan in addressing this issue. The  Japanese Federation of the Blind, the Japan Automobile Manufacturers Association, and Japan’s transportation ministry have already met twice to discuss the issue, and are going to present recommendations by the end of the year on how sounds should be emitted by electric, hybrid and other vehicles that are becoming "too quiet." The only constraint is that the sound can't be too close to a car horn.

Bloomberg News ran this article earlier this week about Nissan engineers coming up with for its hybrid/electric cars "a high-pitched sound reminiscent of the flying cars in (the 1982 movie) 'Blade Runner.' "

The car's sound system would turn on automatically when the car starts and shut off when it reaches 20 kilometers per hour (12 mph), Nissan says. At higher speeds, tire noise provides enough audible clues.

The Washington Post published a story today on the subject as well. This story has an informative graph showing just how quiet a hybrid is in comparison to a conventional car.

At zero miles per hour (mph), a conventional car emits about 50 decibels of noise - the hybrid basically zero. At 6.2 mph, the conventional car emits about 58 decibels, the hybrid 50. They are virtually identical (61 vs. 60 decibels) at 12.4 mph.

The Post story quotes Robert Strassburger, vice president for vehicle safety at the Alliance of Automobile Manufacturers, as saying, "Frankly, we've been working for 30 years to make cars quiet -- never thinking they could become too quiet." This point was also made by Nissan engineers in the Bloomberg story.

The Post story also says that Nissan engineers are concerned about driver reactions to the artificial sound generated by a hybrid or electric car. Some drivers, for instance, complained that the generated sounds made them sleepy or irritated.

Just what we need - noise induced driver rage.

The Bloomberg article says that Tokyo-based Datasystem Co. now makes a device selling for 12,800 yen ($140) that emits 16 different sounds including a cat’s meow, a cartoon-like "boing" and a human voice saying, "Excuse me."  The article didn't say whether the "excuse me" was in a polite or aggressive tone of voice. I suppose you can tune it.

I don't think I would be all that happy, though, with a hybrid car creeping up behind me while I am riding my bike blaring "Excuse me, Excuse me, Excuse me" or "Boing, Boing, Boing."

As the Post story notes, the proliferation of different sounds could quickly get out of hand without some sort of regulation, although Nissan engineers think that a hybrid or electric car's sound could add to its sales/marketing allure. I am sure all other car manufacturers are thinking the same thing.

Okay, Risk Factor readers, here's your chance to show off your creativity.

What sounds do you think electric or hybrid cars should make when they are traveling at slow speeds that can both enhance safety as well as driving/marketing appeal?

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