Minecraft wiki entry for Sculk_Shrieker, associated text: Sculk shriekers can "shriek" after being activated, which can happen by a player stepping on it, triggering a nearby sculk sensor, or powering it with redstone. The shrieker shrieks for exactly 90 game ticks (4.5 seconds). After the shrieking ends, all players in Survival mode within 40 blocks are given the Darkness effect for 12 seconds. Sculk sensors pass on the warning to shriekers only if the sound comes from a player action.