US Patent 9227567 Operation notification sound emission device for vehicle

A vehicle travels with a traveling electric motor controlled with a first control device. A synthetic circuit receives a driving signal from a second control device, which is for controlling another electric motor distinct from the traveling electric motor. The synthetic circuit synthesizes, according to the driving signal, the operation notification sound imitative of a motor sound emitted from the traveling electric motor. An emission unit emits an operation notification sound synthesized by the synthetic circuit to notify the vehicle being in an operation state.