At the Plug-In 2008 Conference & Exposition this week, one company has a solution for a safety concern about electric and hybrid vehicles. Enhanced Vehicle Acoustics (EVA), a Santa Clara, California-based company notes that already eight states and two senators are proposing to increase emitted sound requirements for potentially silent-running vehicles. EVA summarizes that “the absence of acoustic cues currently produced by combustion engines poses a public safety threat to pedestrians, cyclists, children and animals.”

EVA, which has received seed funding from the National Federation of the Blind, has developed a speaker system that mounts externally underneath any EV or hybrid vehicle such as a Toyota Prius that sometimes runs or idles on battery power alone. Controlling the speaker system is a small, embedded computer that monitors what the vehicle is doing - accelerating, slowing, turning, or idling. The computer then sends programmed sounds to one or more speakers on the appropriate side of the car, providing audible cues to unwary pedestrians. Each independent sound is designed to be a psychological clue about the vehicle’s speed and direction. EVA says this increases safety at a fraction of the overall sound output of an ordinary combustion engine vehicle.

The sounds EVA demonstrated at the exposition were acoustically equivalent to a combustion engine doing its thing - accelerating or idling, for example. However, EVA also said that it has already begun working with manufacturers to develop sounds specifically attributable to their brands. Car companies already spend considerable money mechanically engineering the sound of their door slam. Porsche strives for a distinctive rev from its exhaust pipes. Would Porsche consider an electronic match for their 2009 Cayenne Hybrid?

Since the sound files are simple MP3s, personalization seems inevitable, just as people have embraced cellular ringtones. I’m sure at least one early Aptera owner will fly by sounding like he’s driving the Jetson-Mobile. What would you want your vehicle to sound like?