US Patent 9870703 Pedestrian warning system providing adjustable acoustic indications

Systems and methods are disclosed for a pedestrian warning system. An example disclosed method to simulate noise for an electric or noise-dampened vehicle to warning pedestrians includes producing a first sound at a first frequency range from a first sound generator located at a front of the vehicle. The method also includes producing a second sound at a second frequency range from a second sound generator located under the vehicle. Additionally, the example method includes adjusting the acoustic characteristics of the first and second sounds based on vehicle motion data.