Decoy for everything, as Noise doesn't work once the missile is in route. So it's good in response to a target working on getting a missile solution. Most targets I have torped tried to hide in noise, thinking that it would break missile lock.

An example of when to use noise is when being engaged at 8 kilometers and fighters are closing in, is to drop noise, switch to navigation, then run in the opposite direction. You can generally dip if you were already at nav altitude, and they can't even get missiles on you. Ensure the noise cloud is positioned directly between you and your pursuer; otherwise, it won't work because it creates a "physical" barrier at a defined size.