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Lotus Sound Synthesis Technology  (Source:
Device makes the Prius sound like a Lamborghini

Electric vehicles are hot right now and for the most part people see them as great for the environment and a welcome addition to the roads around the country. However, there is a down side to the electric vehicle -- other than a short range -- and that is that they make virtually no noise.

To many drivers, a silent car is a good thing and if electric cars take over the roads in the decades to come, the thought of traffic jam in near silence is much better than the loud idling and sound of combustion we get today. However, for those who are blind and for bicyclists, electric cars can be dangerous.

The Toyota Prius is a good example; when it travels at low speeds and runs on battery power without the combustion engine, it is virtually silent. Without being able to hear an electric car, the visually impaired could step out in front of the vehicle without knowing it was even there.

Congress thinks that the low noise levels of electric cars could be such of a hazard that a bill was introduced to require a minimum sound level on all cars produced for America.

If the bill is made into law, Lotus stands to make a bundle on new technology that it has been demonstrating to address the specific issue of noise -- or lack thereof -- on electric and hybrid vehicles. The technology is called Lotus Sound Synthesis and in essence it is nothing more than a sound system to make sounds pedestrians can hear. Lotus connected the system to a stock Toyota Prius to demonstrate the technology.

The system consists of a 300-watt speaker, a throttle position sensor, amplifier, and synthesis controller. The system would produce engine sounds that would rise and fall -- just like the sounds of a combustion engine -- during acceleration. Lotus says that when the combustion engine kicks in, the speaker system automatically turns off. The speaker itself is a waterproof unit mounted near the cars radiator and according to Lotus the driver hears virtually no sound. The sound could reportedly be made to mimic various engines.

Wired quotes Mike Kimberly, CEO of Group Lotus saying, "We hope that legislators introduce minimum noise requirements for vehicles to encourage the adoption of technologies, such as ours, which will ultimately increase pedestrian safety."

The Toyota Prius isn’t the only car that could benefit from Lotus' system. Honda is bringing the Insight back in 2010 and Tesla has its Roadster on the streets now as well.

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By Some1ne on 8/7/2008 3:35:13 PM , Rating: 3
They're definitely not silent, but they are much quieter than most other vehicles. Hearing one under ideal conditions is not a problem, but it's much easier for the sound of a Prius to be drowned out by background noise than it is for most other vehicles. For example, if you go and stand by a quiet intersection that is lightly trafficked, of course you'll have no problem hearing the Pruis come and go. However, if you go and try the same thing at a busy intersection inside of a large city, where there is background noise from all the non-hybrid vehicles, and other pedestrians talking to each other, and so on, it can be virtually impossible to audibly detect a Prius. I walk to/from work every day, and there have been several occasions where I wasn't able to hear a Prius approaching (a couple times at intersections, and once when one was backing out of a parking space), and only noticed it once I saw that it was moving. And I wasn't listening to headphones or anything else, the small amount of noise that the Prius does make was just drowned out by the ambient background sounds.

So the issue isn't that these cars are "silent", it's that they are so quiet that they are very easily drowned out by background noise. It's not that you'll never hear one, but there are definitely times when you won't, especially in areas with lots of background noise. I think it's a legitimate concern, as even if 9 times out of 10 the blind person hears the Prius, what about the other 1?

By ChronoReverse on 8/7/2008 3:44:20 PM , Rating: 4
Why on earth would you step blind onto a busy intersection without more confirmation than simply hearing?

When I'm at city cruising in my Matrix, the engine is very quiet as well. Someone who's listening for it in traffic wouldn't be able to discern it either.

By Some1ne on 8/7/2008 5:09:25 PM , Rating: 2
I wouldn't, because I'm not blind. But a blind person might. Have you never seen one walking around? They value their independence, and can actually be quite effective at getting themselves around, even in busy/heavily trafficked areas. And they pretty much have to step blind into the intersection, relying on auditory cues to know when it's safe.

By ChronoReverse on 8/7/2008 5:42:41 PM , Rating: 2
Auditory cues that aren't reliable even with non-(hybrid/electric) cars. And that's being generous.

That is to say, if a normal small car can't really be heard over the din of busy traffic, what difference would it make that an electric/hybrid car is quieter?

By lightfoot on 8/7/2008 6:28:34 PM , Rating: 4
Clearly every car must be louder than every other car, that way none of them get drowned out.

"Everything louder than everything else." - Meat Loaf

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