Prius Growing Noisier to Warn Pedestrians Toyota offers 'humming device' to help people hear hybrid coming By Rob Quinn, Newser Staff Posted Aug 24, 2010 4:17 AM CDT 7 comments Comments Prius hybrid vehicles are displayed at Toyota Motor Corp.'s showroom in Tokyo. (AP Photo/Itsuo Inouye, File) (Newser) – Prius drivers worried about mowing down pedestrians who can't hear them coming are being offered a chance to make their cars noisier. Toyota is selling a $150 device that makes a humming noise that's about as loud as a regular car's engine, AP reports. The speaker system is designed to fit under the hybrid car's hood. Use of the device will be voluntary. It goes on sale in Japan—where there have been many complaints about the dangers of silent cars—later this month The company is considering also offering the device in the US and other overseas markets. US government research released last year found that hybrids are twice as likely as cars with conventional engines to be involved in low-speed pedestrian accidents.