A "kok" sound is hear when the car is started and the brake pedal is pressed, this is due to the electronic linkage between the braking system and the automatic transmission. The solenoid valve open and make the "kok" sound the the brake pedal is pressed, only then the gear shift lock is release and the gear can be shift to other mode now, it is normal condition
This is normal as there is electronic linkage between car braking system and automatic transmission