In recent years, electric automobiles employing batteries as a drive power source and hybrid cars employ the batteries as partial drive power source have become popular. When such an automobile uses the battery as the drive power source to drive, the drive noise level outside of the vehicle becomes dramatically lower as compared to those from a conventional gasoline vehicle. As a result, it may happen that a pedestrian or a cyclist does not notice a vehicle approaching to them from outside his field of view. The occurrence of the situation is a serious traffic safety problem.
Due to this, a technique has been proposed for outputting a running noise corresponding to the running condition of the vehicle outside the vehicle (see Patent Document #1, hereinafter, it is referred to as “prior art #1”). In the technique of the prior art #1, the running noise is output outside the vehicle ahead or the like through a speaker for generating a traveling signal based on the detection results of the vehicle speed, the rotational speed of the motor as the power source, the accelerator position, and so on. Then, it is controlled whether the traveling sound is output or not, depending on a region type through which the vehicle is traveling.
Moreover, a technique has been proposed (see Patent Document #2, hereinafter called the “prior art #2”) for automatically warning a pedestrian existing ahead in a traveling direction of the vehicle, although it is not the technique for outputting a vehicle-evocative sound such as a running noise that corresponds to the running condition of the vehicle or the like. In the technique of the prior art #2, a subject presents ahead in the traveling direction of the vehicle are detected. If the subject is detected, the subject is warned by using a warning sound outputted from the speaker.