Sound is also a key factor. Fisher essentially has six movement speeds: two when crouched, two when standing, and then a free-running-like Active Sprint mode for both crouched and standing. According to Redding, any movement is going to generate a small noise event. The severity of that event will change depending upon the selected difficulty level. In realistic or perfectionist mode, anything above the crouched, slow walk will create noise. As Fisher increases speed, the radius of detection widens. Of course, if he sprints, enemies will hear him no matter what.
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According to Redding, different materials will make different noises, and ambient sound is a very minor factor, but Blacklist isnt requiring players to keep an eye on a sound meter at all times.