A motor vehicle and/or water craft horn, comprising: at least one capacitor (C2) of about 220-10000 μF connected in parallel at the input terminals of the horn power supply to eliminate electromagnetic interference caused by electromagnetic radiation, conduction, and coupling. Also provided are a method of eliminating motor vehicle and/or water craft horn electromagnetic interference, an electronic device for using on a motor vehicle and/or water craft, and a motor vehicle and/or water craft. The present invention solves the problem of overrun out of limit of conducted emission (CE) and radiated emission (RE) when a motor vehicle or water craft uses a horn for CIRS 25 testing, thus enabling the horn EMC index to meet the standard.