Maybe as well as an audiable signal a radio signal can be emitted. Cars hear this radio signal and play a horn inside to the driver. Eventually when this is sup

Maybe as well as an audiable signal a radio signal can be emitted. Cars hear this radio signal and play a horn inside to the driver. Eventually when this is supported by all cars the outside horn can be made quieter (just for nearby pedestrians) as penetration through a different car that is playing loud music is no longer an issue. Of course the depreciation period for this is enormous.