Click above for gallery of Lotus' Safe and Sound Hybrid

Hybrid vehicles have the potential to save a few bucks at the pump, but advocates for the blind have continued to warn about their potential harm to the hearing impaired. Lotus' automotive consultancy arm is trying to avert the risk of hybrids quietly running in electric mode with its "Safe and Sound" demo car.

This specially equipped Toyota Prius has been fitted a waterproof speaker mounted above the radiator that can emit a sound similar to a flat-six or V8, based off the vehicle's speed and throttle position. Once the internal combustion engine kicks in, the system is muted, allowing the 1.5-liter inline four to sing its siren song.