In most cases I have found buzzing sounds are created from heat shields. It would be most audible in the center console as the shifter will conduct the noise into the passenger compartment. The noise is probably related to a specific engine RPM and created by engine/drivetrain harmonics. The use of the AC could shift the balance of the engine to eliminate the buzzing. If a shield is a problem you should be able to hit each shield with your fist and hear a resonance. But I am speaking of vehicles in general and not specifically of yours.
Good luck with the Kia.
Good luck with the Kia.
