A horn of vehicle is necessary equipment for all means of communication on road, and the annual consumption is very large. The utility model provides a horn which is controlled by an electronic device. The horn of the utility model is not provided with contacts, the tone is changeable, and the tone can be automatically changed or intermittently played. Thus, the operation is simple, and the frequency of actions of a horn relay is reduced. When automatically changing the tone, a bass tone can be created by pressing with a short time, and a high tone can be automatically converted by pressing with a longer time. Parameters can be properly selected, and then long and short 'Du-Du' tones can be created by continuously pressing. In addition, the tone can be once changed at a time, a short tone can be created at first, and then the tone is converted into a long tone until a hand moves away. Therefore, the horn is a multifunctional automatic acoustic horn, and the cost is similar to normal non-contact horns.