How do I create a noise radius and a response?

I want to make a noise radius and a reaction to that.

For example if my Player shoots I want to set up a noise radius and if the Monster is in that radius it reacts because it hears the noise.

Is there a tutorial how to do that?

I can think of a couple of easy ways to do this... none of which use the audio events.

One - Make an instance variable in your enemies called something like "DetectedPlayer" set to no by default and whenever your fire a weapon call a function that simply scans for enemies within range using pixel distance or other method and then set them to yes/detected and run their go kill player AI event.

Two - poor mans way...(capx provided) Make an invisible cube/rectange/circle.. etc called RifleRadius... ShotgunRadius.. etc.. and when a gun is fired spawn the invisible sprite radius thingy on your players gun fire image point and use an On-overlap event with your enemies it sets them to kill player mode and then deletes itself.

Thanks.