Although many people like the fact that electric cars don't produce any engine noise, this means that blind pedestrians can't always hear the things coming. Having the cars emit a warning sound when traveling at slow speeds is one solution, and a new system could help keep that sound from being any louder than necessary.
In a number of countries, electric vehicles are already required to be equipped with slow-speed warning sound systems, or they soon will be. The problem is, if that sound is loud enough to be heard in busy downtown traffic, it will be unpleasantly loud in quieter environments such as residential neighborhoods.
With that in mind, a team from Norway's SINTEF research group is developing what's known as an "adaptive sound" system. The technology monitors the ambient noise levels of the environment utilizing a car-integrated microphone, and then responds by raising or lowering the volume of the warning sound accordingly.
In order to determine just how loud that sound needs to be, the researchers drove an electric car equipped with the system down a quiet stretch of road, which blind volunteers sat along side of. Loudspeakers produced traffic noise at various levels, which the adaptive sound system responded to. As soon as the volunteers were able to hear the car's warning sound, they pressed a button to indicate that it was loud enough.
"A number of car manufacturers, including Nissan, General Motors and Renault, have shown interest in the results of this project," says lead scientist Truls Berge. "Norway has the highest density of electric vehicles in the world, so it's natural that electric car manufacturers look to us with regard to traffic safety and research in this field."
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