I think you’re mixing up territorial disputes between predators and hunting of prey. For example, in Alien humans are mostly the prey and in those cases the aliens are very quiet. They make noises when being attacked though.

It is like that in many movies. When a predator is disturbed by another predator or large animal/object like a human or a human in a car, it may decide to make noise in order to defend it’s territory without having to risk injury.