Sound generating system for environment friendly vehicle and a method for controlling the system

1. A control method of an environmentally-friendly vehicle sound generator apparatus, the method comprising:

a providing step of providing an environmentally-friendly vehicle sound generator apparatus including: a vehicle state sensing unit for sensing an operation state of a vehicle; a sound source storage unit for storing a plurality of operating sounds that can be output according to the operation state of the vehicle in the form of a sound source data; a sound source playback unit for selecting at least one of the operating sounds stored in the sound source storage unit, and playing back the selected sound source output from the sound source storage unit; a sound source amplification unit for amplifying the operating sound played back by the sound source playback unit; a sound output unit for outputting the operating sound amplified by the sound source amplification unit; and a control unit for receiving a sensing signal from the vehicle state sensing unit and controlling the operation of the sound source playback unit so as to play back the operating sound in different playback methods in such a manner as to control and change the operating sound according to the received sensing signal, wherein the vehicle state sensing unit senses a vehicle speed, and wherein if it is determined according to a vehicle speed signal of the vehicle state sensing unit that the vehicle speed reaches a preset speed range, the control executes a fade-out function in consideration of a vehicle speed and a time after the vehicle speed enters a speed over the preset speed range; and

an operating sound execution step of allowing the control unit to determine whether or not to generate an operating sound of the environmentally-friendly vehicle according to the vehicle operation state sensed by the vehicle state sensing unit, and outputting one or more sound sources, selected among the sound sources stored in the sound source storage unit, as the operating sounds through the sound output unit,

wherein the operating sound execution step comprises a fade-out step (S 60 ) of fading out the output of the sound output unit, if the vehicle speed reaches the preset speed range, with at least one of a preset ratio corresponding to the vehicle speed and a preset ratio corresponding to an elapsed time after the vehicle speed enters a speed over the preset speed range,

wherein the fade-out step (S 60 ) comprises:

a fade-out mode determination step (S 61 ) of comparing the vehicle speed with a preset fade-out mode determination speed; and

a fade-out mode execution step (S 63 ) of executing the fade-out mode determined at the fade-out mode determination step (S 61 ).

2. The control method according to claim 1 , wherein the fade-out mode execution step (S 63 ) comprises a fade-out speed mode (S 65 ) of reducing, if the vehicle speed is lower than the preset fade-out mode determination speed, the output of the sound output unit at a preset fade-out speed ratio according to the vehicle speed.

3. The control method according to claim 2 , wherein the fade-out speed mode (S 65 ) comprises:

a fade-out vehicle speed calculation step (S 651 ) of updating and calculating a fade-out vehicle speed by averaging the vehicle speed input during a preset holding time; and

a fade-out speed output control step (S 653 ) of reducing the output of the sound output unit at the preset fade-out speed ratio according to the fade-out vehicle speed.

4. The control method according to claim 1 , wherein the fade-out mode execution step (S 63 ) comprises a fade-out time mode (S 67 ) of reducing, if the vehicle speed is higher than the preset fade-out mode determination speed, the output of the sound output unit at a preset fade-out time ratio according to a time elapsed after the vehicle speed enters a range higher than a preset speed.

5. The control method according to claim 4 , wherein the fade-out time mode (S 67 ) comprises:

a time counting step (S 671 ) of confirming a time elapsed after the vehicle speed enters a range higher than the preset speed; and

a fade-out time output control step (S 673 ) of reducing the output of the sound output unit at the preset fade-out time ratio according to the elapsed time.