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A Sound Proposal for Electric Vehicles

An article on CNNMoney.com published today, reports that automakers and advocates for the blind have agreed on a plan to add sounds to electric and hybrid vehicles when operating at low speeds, to help alert pedestrians to their presence.

This is a good step, but the sound must be chosen and implemented very carefully! A good sign is this part of the story:

The sound couldn’t be just anything. For instance, vehicle owners would not be able to “customize” the sound of their car the same way they can download ringtones for cell phones. That’s specifically prohibited in the proposed rule.

Instead, car manufacturers would provide an approved sound or set of sounds for a given make and model of car.

It is imperative that the sound not seem similar to other important sounds, such as sirens, backup alarms, pedestrian crosswalk sounds, and a host of other sounds. In fact, the interaction of these sounds is important and frequent enough that they should be designed together, so that when all are present simultaneously, pedestrians aren’t dazed and confused by the cacophony.

At the present time, none of these existing sounds–emergency vehicle sirens, backup alarms, and crosswalk tones–are well-designed, and they are actually so poorly designed that their very nature has caused injury and death. Emergency vehicle sirens have no directionality, so that when multiple vehicles are arriving from different directions, it is impossible to know what action must be taken to get out of their way. Backup alarms also have no directionality, and additionally are of a frequency within the range of common hearing loss. And crosswalk tones are so inconsistent that they can differ from one block to the next, and can make it more confusing for sight-impaired pedestrians to cross than without the tones.

Some of the existing research tested multiple vehicle sounds, including engine, horn, hum, siren, whistle, and white noise. The full report contains a great deal of guidance, but even it didn’t involve the use of actual vehicles, just video recordings of a Prius synched with the test sounds.

This is a golden opportunity to get all of these sounds designed and interacting properly, but it will require a significant amount of research and testing. Existing research has provided hints at the directions each of these signals should take in a redesign, but no research has been comprehensive enough to make it safe to lock new sounds into federal legislation.

Posted in Standards.


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