Beyond Enemy Lines uses a movement based noise calculation system. Each movement or action will result in a noise with a different volume calculated on your movement speed and interaction material. Not even walking or shooting a gun produces a noise, even reloading the gun, opening a door or toggle a switch cause noises. It depends on you how you use the noise to your advantage, whistle to lure guards into your direction or distract them with other noises. Think twice before you do anything or the noise will be your bigges enemy!