Enemy can hear sounds from far away

[Romulator]

It might be an idea to backup your grunt here, or if you want a deaf grunt throughout your entire Amnesia gameplay then we can do that :3

Seeing as you have the Level Editor, I'll assume you have the Model Editor too. Open your grunt in that which has the ActivationDistance at 100, and turn the HearVolume number within the User Defined Variables (Settings drop down menu up the top) down to 0 (and if this doesn't work, put it up to like, 100).

Also, if you don't want the grunt to disappear after the last pathnode (I THINK he'll just stand there though), untick AutoRemoveAtPathEnd, also in the User Defined Variables. That should keep him around as well.

In terms of Game Mechanics...

Spoiler below!

A grunt, as stupid as they may seem as holding a large drawer over your face says "Hey, I'm invisible!" and gets them to walk away, are responsive to sound and will investigate. A monster will attempt to make it's way to the source of the sound, often relying on pathnodes or sometimes simply walking towards the source.

This is one small aspect of the whole surreal atmosphere of Amnesia in being able to make it tougher. Seeing as enemies have the intelligence to spot you in the crowd of boxes, barrels and bricks (so long as you're a distance less than 20 (in-game metres) away), and still be able to hear you from a distance, they will come running.

The grunts however will only respond to a certain volume of sound, which is by default 0.55. Anything above this, the monster will hear and investigate. Tossing crap into the water against the Kaernk is quite loud, which is why it approaches you whenever you make a splash.