Here is an idea. Knocking on stuff. Sort of like flushing out zombies or alerting players in a house, a friendly is there. Two types of taps. A soft one that alerts very close by zombies, but players can hear them. A loud knock. example Before I enter the house, I go in back and do a loud knock on the back door. The zombies respond and moan. They move to the sound. If far away, they are unlikely to attack the door. Soft knock has a 50 50 chance close by zombies attack the door. I move to the front door as they investigate. Opening the door and ambushing the zombies before they can turn to attack. Knocking can be done on other objects.