Having grown up with the roar of gasoline-powered engines, most people rely not only on their eyes, but also their ears when detecting the danger of an oncoming vehicle. The quiet whirring of an electric a hybrid vehicle operating at low speeds isn’t enough to alert pedestrians of the vehicle’s approach and poses particular risks to the blind. To address this problem Toyota has announced that it will begin selling an onboard audio device that provides alerts pedestrians to the presence of quiet vehicles, such as its gasoline-electric hybrid Prius.

To meet new guidelines from Japan’s Ministry of Land, Infrastructure, Transport and Tourism for hybrid and near-silent vehicles, Toyota will begin selling the device in Japan from August 30 for retrofitting on its third-generation Prius vehicles. When the Prius is operating as an electric vehicle at speeds up to approximately 25km/h (15mph) the onboard device automatically emits a synthesized sound of an electric motor.

The sound, which Toyota says is “aimed to alert but not annoy,” rises and falls in pitch relative to the vehicle’s speed to help indicate the vehicle’s proximity and movement. Maybe some bright spark will come up with a way to hook up the device to a SoundRacer to give their Prius some real volume.

Toyota also plans other versions of the device for use in gasoline-electric hybrids, plug-in hybrids, electric vehicles as well as fuel-cell hybrid vehicles planned for launch.