Amplifying Safety in Hybrid Cars The relative silence of hybrid cars poses safety concerns for visually impaired pedestrians who rely on sound cues from oncoming traffic. Two Stanford graduates have developed a system that broadcasts specific sounds based on what the car is doing.
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Amplifying Safety in Hybrid Cars

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Amplifying Safety in Hybrid Cars

Amplifying Safety in Hybrid Cars

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  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

GUY RAZ, host:

And now for a little demonstration out on the blacktop.

(Soundbite of car moving)

RAZ: That's the sound of a normal car going about 20 miles an hour here in downtown in Washington, D.C. where I'm standing. Now, take a listen to this car that's about to pass. It's also traveling at roughly the same speed.

(Soundbite of silence)

RAZ: Did you hear much? Neither did I. It's because the car that just passed, it was a hybrid, and as long as you stay under 25 miles an hour, hybrid engines, like this one, barely make a peep. No sound, no headaches, right? Wrong. Because if you're blind or a small child or just a big absent-minded, the silence of a hybrid engine might actually be dangerous, so dangerous that the National Federation of the Blind asked the smartest students in America to tackle the problem.

And one of those students is recent Stanford graduate Everett Meyer, who helped invent something that could put the hum back in the hybrid.

Mr. EVERETT MEYER (Stanford Graduate): Well, the device itself is a speaker-based system. It's audio speakers like you would find in outdoor speakers -they're very robust. They're placed on the wheel wells on the vehicle. And it sounds essentially like a vehicle except for the sounds are more intelligently projected.

For example, if a person is in drive mode and moving forward, the sounds are only projected in the forward direction, which is very different from the combustion engines. If the driver decides to turn left or right, the sounds changes on the left or right appropriately. So, it minimizes noise pollution and maximizes acoustic information for pedestrians.

RAZ: Well, listen to some of that sound that would be emitted from these speakers. This is a recording, I think, of the hybrid accelerating.

(Soundbite of engine running)

RAZ: Now, that to me sounds like George Jetson's car…

(Soundbite of laughter)

RAZ: …or like a ride in Disneyland. But that's the sound of a hybrid accelerating? I mean, this is an invented sound that you guys made, right?

Mr. MEYER: It's an engineered sound on the part of our sound audio engineer, Brooke Reader, to lay out the landscape of what's possible. And when you actually put that on a car with the speakers in place, it does sound actually very realistically and very…

RAZ: How is that?

Mr. MEYER: …(unintelligible).

RAZ: Is that because of the vibration of the car and the wheels and…

Mr. MEYER: Exactly. The acoustic properties change when you're actually on the frame and you're dealing with echoes from the wheel well, etc.

RAZ: Now, you guys had just three sounds that were mixed together to create this hybrid noise. Run through what they are and then we'll play them.

Mr. MEYER: Yes. So, again, Brooke Reader, our audio engineer, created these sounds and they have different purposes.

(Soundbite of low humming)

Mr. MEYER: So, for example, the flute sound gives you a sense of comfort and it may help localize where the vehicle is because there's this constant tonality.

(Soundbite of mid-level humming)

Mr. MEYER: The chanting sound has a more emotive quality and can really capture that car identity or those car tones.

(Soundbite of low whistling)

Mr. MEYER: And the last sound is a specified frequency sound, which is really peppered in there at key frequencies to allow individuals to know, hey, this is a vehicle.

RAZ: Now, I've got to say I'm pretty sure we're going to get emails from listeners saying, you know, there's already plenty of noise out there. I mean, aren't you guys just sort of adding to the noise pollution? I mean, shouldn't be hybrid drivers just be more careful and, you know, watch out for pedestrians?

Mr. MEYER: Well, there's a difference between noise and sound and we view our system as producing sounds which have a purpose. Unlike combustion engines that make noise, our sounds are explicitly designed for pedestrian safety. And the overall sound level experienced by pedestrians coming from our vehicles would be much, much lower than even the quietest combustion engines.

RAZ: So, I mean, are we going to be hearing, like, the Macarena coming out of cars?

(Soundbite of laughter)

Mr. MEYER: No Van Halen, no. You may have some musical elements but you won't have music itself.

RAZ: Everett Meyer is one of the founders of Enhanced Vehicle Acoustics in Santa Clara, California.

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