October 19, 2017 |

Deregulating the Unregulated: What’s up with Inaudible Electric Cars?

She stood at the curb looking forlorn and then turned slightly away. When she turned back he was gone. Where had he gone? Would she ever see him again? Why didn’t she realize he had slipped away?

Is this an opening scene from a romance novel? Could be. But actually, it’s a real life story repeated over and over when he drives an electric or hybrid car. These car owners can appear one minute and disappear the next. It’s disheartening, unsettling – but also dangerous!

Since hybrid cars were introduced there has been worry about how quiet they are. This grew out of a concern for the blind, for children, oblivious adults, and our neighborhood animals; rabbits, turkeys, and pets. The National Highway Traffic Safety Administration estimates that some 2,400 pedestrian injuries could be prevented if electric and hybrid cars were required to make noticeable noise when traveling at very slow speeds. Congress actually passed legislation back in 2010 which mandated that these cars emit noise. But the implementation has been stalled, and now the Trump administration may eliminate the requirement altogether.

Isn’t it ironic. The most annoying noise coming from construction sites is often generated by back-up alarms. The government has mandated that trucks emit noise in the form of warning sounds when backing up — to protect someone who might be standing in the path of the truck. But electric cars can start off, or backup, without any warning. Are we sure the driver is looking carefully ahead or behind? Are we sure that a small child or pet isn’t just below the sightline of the driver? Does the car have a backup camera that the driver is alert to?

I certainly wouldn’t advocate for electric and hybrid cars to mimic the backup noise of trucks, but I believe that some additional noise could be added (the NHSTA estimates the cost to be about $130 per vehicle). That’s a small (hidden) price compared to all the safety packages, sound systems, simonizing, etc. that can add to the base price of an automobile.

Let’s think of about what kind of sound we would want to add to vehicles to ensure our safety. Surely not the jingle or an ice cream truck. Perhaps not even the sound of a conventional gasoline engine. At Acentech we have developed a sound evaluation process called a jury study. We gather a set of sounds and a set of individuals and we ask the “jury” to rate the sounds. How appropriate is the sound? How appealing is it? The question is dictated by the particular study. We’ve had jurors rate the sounds for washing machines, convection ovens, and even drones. In those cases, because the sound is integral to the product we can only modify the sound by modifying the product. But for electric cars the possibilities of sounds are wide open. What fun to think about which direction to pursue! What attributes should the sound convey? What image of the car should it emphasize? Or, perhaps, what image of the driver? Maybe, like cell phone ring tones –we could personalize our cars! And come to think of it, have you ever heard the booming of low frequency music coming from a hybrid?

For now, car makers are in limbo. Will the regulations be eliminated, or should they continue to consider how to add noise to their cars? Or, might some manufacturers use noise as a selling point — “we’ve taken it upon ourselves to think about added safety — for the people around you”. Surely owners of electric cars are concerned about the potential danger of having so silent a car. Perhaps this could be a marketing tool — the car dealer who really cares about you, me, and our furry friends!

Author: Gladys Unger

Dr. Gladys Unger has a wide range of experience in acoustics and vibration including environmental noise studies and building vibration. She has been involved in remote monitoring of vibration and…

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