It doesn't take much searching in the PriusChat forums to get an idea of how Prius owners feel about taking their silent "stealth" mode and turning it into a hybrid ice cream truck , and big names in the EV scene such as Chelsea Sexton have weighed in on the What Drives Us podcast regarding the issue. All of that feedback has led us to an announcement by Toyota introducing an "Approaching Vehicle Audible System" for the 3rd Generation Prius. For $150, Prius owners will be able to add a speaker system that goes under the hood of the 3G Prius and produces a bizarre sound that sounds like it was taken from a B-level horror movie. Its use is voluntary in Japan, where it will first be marketed starting August 30th. The noisemaker is "designed to meet new Japanese Ministry of Land, Infrastructure, Transport, and Tourism guidelines for hybrid and other near-silent vehicles." Toyota is considering whether they will offer the system in the US at a later date. According to the Toyota press release, "TMC 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." Video below. Press release after that. TMC to Sell Approaching Vehicle Audible System for 'Prius' Toyota City, Japan, August 24, 2010—Toyota Motor Corporation (TMC) announces that, in line with its efforts to ensure an ever-safer traffic environment, it will begin sales on August 30 of an onboard device designed to alert pedestrians and others audibly to the presence of a quiet vehicle, such as a gasoline-electric hybrid. The device will be available nationwide through authorized Toyota dealers and Toyota genuine parts & accessories distributors for retrofitting on the third-generation "Prius" gasoline-electric hybrid vehicle. The onboard device automatically emits a synthesized sound of an electric motor when the Prius is operating as an electric vehicle at speeds up to approximately 25 km/h. The sound—aimed to alert but not annoy—rises and falls in pitch relative to the vehicle's speed, thus helping indicate the vehicle's proximity and movement. The device is designed to meet new Ministry of Land, Infrastructure, Transport and Tourism guidelines* for hybrid and other near-silent vehicles. TMC 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. Onboard approaching vehicle audible system details Price Compatible vehicle models Function 12,600 yen (Includes consumption tax; does not include installation charge or other incidental fees) Third-generation Prius Emits a synthesized sound of an electric motor to alert pedestrians and others to the presence of a quiet vehicle. *Issued in January 2010 and based on assessments from the Committee for the Consideration of Countermeasures Regarding Quiet Hybrid and Other Vehicles, in which TMC participated as a member of the Japan Automobile Manufacturers Association. The committee began assessing possible countermeasures in July 2009, after hearing concerns of drivers and other people about gasoline-electric hybrids and electric vehicles operating in near silence.