Notification sound control unit of approaching vehicle audible system

A notification sound control unit of an approaching vehicle audible system, generating a signal for a notification sound to be emitted from a sounding device provided in an electric vehicle in which at least part of driving force is produced by an electric motor to outside of the electric vehicle, the notification sound control unit of an approaching vehicle audible system comprising:

• a changing amount determination section that categorizes a status of change in an accelerator opening degree signal among vehicle information signals of the electric vehicle into a plurality of modes and determines to which mode among the categorized modes the status of the change in the accelerator opening degree signal belongs;
• a behavior conversion processing section that processes the accelerator opening degree signal with a delay processing to delay the accelerator opening degree signal based on the mode determined by the changing amount determination section so as to output a processed accelerator opening degree signal;
• and
• a notification sound signal generation processing section that changes a pitch and a volume of a sound element signal outputted from a sound element, based on the processed accelerator opening degree signal, so as to generate a notification sound signal.